Fix ViT-MAE decoder interpolate
Author: xenova
Pull request: yes
Labels: name: run-slow

# What does this PR do?
Similar to #33226, with a fix for the ViT-MAE decoder (see [comment](https://github.com/huggingface/transformers/issues/32410#issuecomment-2293359788)).
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Fixes #32410


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@amyeroberts 


Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_33330). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

I'll add a unit test and then merge 👍

Apologies for the delay - totally forgot about this! 😅 

Before:
```
FAILED tests/models/vit_mae/test_modeling_vit_mae.py::ViTMAEModelIntegrationTest::test_inference_interpolate_pos_encoding_custom_sizes - RuntimeError: The size of tensor a (257) must match the size of tensor b (256) at non-singleton dimension 1
```

After:
```
34 passed, 114 skipped, 4 warnings in 8.80s
```

---

~@amyeroberts can we trigger slow tests and then I'll merge? :) Thanks!~ nvm I was able to do it! Just re-requesting review to check that I did the unit tests right.

Hey! 🤗 Thanks for your contribution to the `transformers` library!

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