Remove GPT-2  tokenizer dependancy from Deberta Tokenizers
Author: RamitPahwa
Pull request: yes

# What does this PR do?
Hi @sgugger 
Related to #19303 , 
- the GPT2Tokenizer dependency has been removed from DebertaTokenizer
- the GPT2TokenizerFast dependency has been removed from DebertaTokenizerFast

I ran` pytest tests/models/deberta/test_tokenization_deberta.py` which passed 
Thanks for reviewing!

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Comments:
_The documentation is not available anymore as the PR was closed or merged._

Hi @sgugger 
Please review the above PR when you get a moment.

I raised a Clean PR #19551 for this work will close once that is merged, @sgugger Please review