Removed XML and Bert dependency from Herbert tokenizer 
Author: harry7337
Pull request: yes

# What does this PR do?

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Fixes #19303. Removed the dependency of herbert(slow/fast) tokenizer on bert and xml.


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Pinging @sgugger for this issue!
Black seems to be working fine on my system, but shows errors in the automated tests for files that I haven't modified. For example: wav2vec2 and blenderbot_small have only style changes but is failing a run_tests_tf and run_tests_torch respectively. Let me know if this is ok!

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Models:

- albert, bert, xlm: @LysandreJik
- blenderbot, bart, marian, pegasus, encoderdecoder,  t5: @patrickvonplaten, @patil-suraj
- longformer, reformer, transfoxl, xlnet: @patrickvonplaten
- fsmt: @stas00
- funnel: @sgugger
- gpt2: @patrickvonplaten, @LysandreJik
- rag: @patrickvonplaten, @lhoestq
- tensorflow: @LysandreJik

Library:

- benchmarks: @patrickvonplaten
- deepspeed: @stas00
- ray/raytune: @richardliaw, @amogkam
- text generation: @patrickvonplaten
- tokenizers: @n1t0, @LysandreJik
- trainer: @sgugger
- pipelines: @LysandreJik

Documentation: @sgugger

HF projects:

- datasets: [different repo](https://github.com/huggingface/datasets)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Examples:

- maintained examples (not research project or legacy): @sgugger, @patil-suraj
- research_projects/bert-loses-patience: @JetRunner
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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_19407). All of your documentation changes will be reflected on that endpoint.

Hi there! Thanks a lot for working on this, but your PR shows a diff of 577 files when it should just be the two tokenizer file you are touching.
I think it might be because you have a different version fo black that we are using in your environment. Could you try doing `pip install -e. [quality]`?

Superseded by #19410