GPTTokenizer dependency removed from deberta class
Author: RamitPahwa
Pull request: yes

# What does this PR do?
Hi @sgugger, I am raising this clean PR for PR #19421
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._