Bugfix converting added tokens before save
Author: amirza1
Pull request: yes

convert_added_tokens is called on every save.
It also modifies the AddedTokens by performing pop, which prevents saving a tokenizer more than one time

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Fixes # (issue)


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Comments:
cc @ArthurZucker @itazap 

hey @amirza1 ! Thanks for opening this PR!! 🤗  Can you please link the issue # or provide a small code snippet / reproducer for the bug? Thank you! 😊 

I apologize, we can probably close it, it appears the latest versions of the code do not have this issue. 

No worries! Thank you for the quick follow up! Closing 🤗 

A closer inspection shows that the rust version of tokenizers works. The bug is still in the code, so it's up to you :)

Can you please provide:

- a reproducer 
- observed behaviour
- expected behaviour

Thank you!