Remove typing-extensions from deps

[akx]

Pull Request check-list

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• Do tests and lints pass with this change?
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Description of change

Removes typing-extensions from dependencies.
It's not used, and this library requires Python 3.8+.

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (2f88840) 91.84% compared to head (8ed507f) 91.85%.
Report is 5 commits behind head on master.

Files	Patch %	Lines
redis/asyncio/connection.py	83.33%	1 Missing ⚠️

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3146   +/-   ##
=======================================
  Coverage   91.84%   91.85%           
=======================================
  Files         128      128           
  Lines       33232    33272   +40     
=======================================
+ Hits        30523    30561   +38     
- Misses       2709     2711    +2     

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