[tokenizer] Updates huggingface tokenizer to 0.21.0

[xyang16]

Description

Brief description of what this PR is about

• If this change is a backward incompatible change, why must this change be made?
• Interesting edge cases to note here

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.90%. Comparing base (c0d3a37) to head (50f1c86).
Report is 2 commits behind head on master.

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HEAD has 1 upload less than BASE

Flag	BASE (c0d3a37)	HEAD (50f1c86)
	2	1

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3572       +/-   ##
=============================================
- Coverage     72.43%   58.90%   -13.53%     
+ Complexity     7421     5862     -1559     
=============================================
  Files           674      674               
  Lines         33087    33087               
  Branches       3526     3526               
=============================================
- Hits          23966    19490     -4476     
- Misses         7490    12117     +4627     
+ Partials       1631     1480      -151     

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