Fix incorrect return annotation in asyncio.lock

[JelleZijlstra]

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Description of change

NoReturn should be used only when the function never returns. In this case, the awaitable returns None if releasing the lock succeeds, so Awaitable[None] is right.

Noticed this while reviewing python/typeshed#7676

[codecov-commenter]

Codecov Report

Merging #2155 (b452c03) into master (40fdb15) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2155   +/-   ##
=======================================
  Coverage   92.50%   92.50%           
=======================================
  Files         105      105           
  Lines       25191    25191           
=======================================
  Hits        23303    23303           
  Misses       1888     1888           

Impacted Files	Coverage Δ
redis/asyncio/lock.py	99.12% <100.00%> (ø)

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[chayim]

Thank you @JelleZijlstra this is great! We'd love to get everything, properly typed, inserting a py.typed when ready. Keep 'em coming!