Single config attribute for weight tying
Author: zucchini-nlp
Pull request: yes

# What does this PR do?

As discussed with Arthur, we can keep only one of the attributes because both have the same functionality after the "Big refactor"



Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_42815). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

run-slow: bart, d_fine, dab_detr, deformable_detr, encoder_decoder, grounding_dino, longt5, marian, mm_grounding_dino, mt5, pop2piano, rt_detr_v2, switch_transformers, t5, udop, umt5

This comment contains `run-slow`, running the specified jobs: 

models: ["models/bart", "models/d_fine", "models/dab_detr", "models/deformable_detr", "models/encoder_decoder", "models/grounding_dino", "models/longt5", "models/marian", "models/mm_grounding_dino", "models/mt5", "models/pop2piano", "models/rt_detr_v2", "models/switch_transformers", "models/t5", "models/udop", "models/umt5"]
quantizations: []

## CI Results
[Workflow Run ⚙️](https://github.com/huggingface/transformers/actions/runs/20138300391)

### Model CI Report

#### ❌ Failed tests

- [bart](https://github.com/huggingface/transformers/actions/runs/20138300391/job/57798632695):
    tests/models/bart/test_modeling_bart.py::BartModelTest::test_config
    tests/models/bart/test_modeling_bart.py::BartStandaloneDecoderModelTest::test_config

- [d_fine](https://github.com/huggingface/transformers/actions/runs/20138300391/job/57798632725):
    tests/models/d_fine/test_modeling_d_fine.py::DFineModelTest::test_load_save_without_tied_weights

- [grounding_dino](https://github.com/huggingface/transformers/actions/runs/20138300391/job/57798632770):
    tests/models/grounding_dino/test_modeling_grounding_dino.py::GroundingDinoModelTest::test_load_save_without_tied_weights

- [marian](https://github.com/huggingface/transformers/actions/runs/20138300391/job/57798632715):
    tests/models/marian/test_modeling_marian.py::MarianModelTest::test_config
    tests/models/marian/test_modeling_marian.py::MarianStandaloneDecoderModelTest::test_config

- [mm_grounding_dino](https://github.com/huggingface/transformers/actions/runs/20138300391/job/57798632747):
    tests/models/mm_grounding_dino/test_modeling_mm_grounding_dino.py::MMGroundingDinoModelTest::test_load_save_without_tied_weights

- [mt5](https://github.com/huggingface/transformers/actions/runs/20138300391/job/57798632755):
    tests/models/mt5/test_modeling_mt5.py::MT5ModelTest::test_config
    tests/models/mt5/test_modeling_mt5.py::MT5EncoderOnlyModelTest::test_config
    tests/models/mt5/test_modeling_mt5.py::MT5IntegrationTest::test_small_integration_test

- [pop2piano](https://github.com/huggingface/transformers/actions/runs/20138300391/job/57798632704):
    tests/models/pop2piano/test_modeling_pop2piano.py::Pop2PianoModelTest::test_config

- [rt_detr_v2](https://github.com/huggingface/transformers/actions/runs/20138300391/job/57798632829):
    tests/models/rt_detr_v2/test_modeling_rt_detr_v2.py::RTDetrV2ModelTest::test_load_save_without_tied_weights

- [t5](https://github.com/huggingface/transformers/actions/runs/20138300391/job/57798632705):
    tests/models/t5/test_modeling_t5.py::T5ModelTest::test_config
    tests/models/t5/test_modeling_t5.py::T5EncoderOnlyModelTest::test_config
    tests/models/t5/test_modeling_t5.py::T5ModelIntegrationTests::test_small_byt5_integration_test
    tests/models/t5/test_modeling_t5.py::T5ModelIntegrationTests::test_small_v1_1_integration_test



un-slow: bart, d_fine, dab_detr, deformable_detr, encoder_decoder, grounding_dino, longt5, marian, mm_grounding_dino, mt5, pop2piano, rt_detr_v2, switch_transformers, t5, udop, umt5

run-slow: bart, d_fine, dab_detr, deformable_detr, encoder_decoder, grounding_dino, longt5, marian, mm_grounding_dino, mt5, pop2piano, rt_detr_v2, switch_transformers, t5, udop, umt5



This comment contains `run-slow`, running the specified jobs: 

models: ["models/bart", "models/d_fine", "models/dab_detr", "models/deformable_detr", "models/encoder_decoder", "models/grounding_dino", "models/longt5", "models/marian", "models/mm_grounding_dino", "models/mt5", "models/pop2piano", "models/rt_detr_v2", "models/switch_transformers", "models/t5", "models/udop", "models/umt5"]
quantizations: []

## CI Results
[Workflow Run ⚙️](https://github.com/huggingface/transformers/actions/runs/20141816827)

### Model CI Report

#### ❌ Failed tests

- [mt5](https://github.com/huggingface/transformers/actions/runs/20141816827/job/57811617752):
    tests/models/mt5/test_modeling_mt5.py::MT5IntegrationTest::test_small_integration_test



run-slow: mt5

This comment contains `run-slow`, running the specified jobs: 

models: ["models/mt5"]
quantizations: []

## CI Results
[Workflow Run ⚙️](https://github.com/huggingface/transformers/actions/runs/20162193380)

✅ No failing test specific to this PR 🎉 !


run-slow: bart, bigbird_pegasus, blenderbot_small, d_fine, dab_detr, deformable_detr, grounding_dino, led, longt5, m2m_100, marian, mbart, mm_grounding_dino, mt5, mvp, nllb_moe

This comment contains `run-slow`, running the specified jobs: 

models: ["models/bart", "models/bigbird_pegasus", "models/blenderbot_small", "models/d_fine", "models/dab_detr", "models/deformable_detr", "models/grounding_dino", "models/led", "models/longt5", "models/m2m_100", "models/marian", "models/mbart", "models/mm_grounding_dino", "models/mt5", "models/mvp", "models/nllb_moe"]
quantizations: []

## CI Results
[Workflow Run ⚙️](https://github.com/huggingface/transformers/actions/runs/20162737239)

✅ No failing test specific to this PR 🎉 !



run-slow: bart, bigbird_pegasus, blenderbot_small, d_fine, dab_detr, deformable_detr, grounding_dino, led, longt5, m2m_100, marian, mbart, mm_grounding_dino, mt5, mvp, nllb_moe




run-slow: bart, bigbird_pegasus, blenderbot_small, d_fine, dab_detr, deformable_detr, grounding_dino, led, longt5, m2m_100, marian, mbart, mm_grounding_dino, mt5, mvp, nllb_moe



run-slow: bart, bigbird_pegasus, blenderbot_small, d_fine, dab_detr, deformable_detr, grounding_dino, led, longt5, m2m_100, marian, mbart, mm_grounding_dino, mt5, mvp, nllb_moe



**[For maintainers]** Suggested jobs to run (before merge)

run-slow: bart, d_fine, dab_detr, deformable_detr, grounding_dino, longt5, marian, mbart, mm_grounding_dino, mt5, nllb_moe, pegasus, plbart, pop2piano, rt_detr_v2, switch_transformers

This comment contains `run-slow`, running the specified jobs: 

models: ["models/bart", "models/bigbird_pegasus", "models/blenderbot_small", "models/d_fine", "models/dab_detr", "models/deformable_detr", "models/grounding_dino", "models/led", "models/longt5", "models/m2m_100", "models/marian", "models/mbart", "models/mm_grounding_dino", "models/mt5", "models/mvp", "models/nllb_moe"]
quantizations: []

View the CircleCI Test Summary for this PR:

https://huggingface.co/spaces/transformers-community/circle-ci-viz?pr=42815&sha=377fee

## CI Results
[Workflow Run ⚙️](https://github.com/huggingface/transformers/actions/runs/20348772784)

✅ No failing test specific to this PR 🎉 !


Slow tests are ✅  so ig no breaking changes for official ckpts, will merge