Update xtrim type annotation

[richli]

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Description of change

In xtrim(), the maxlen argument may be None if minid is specified, so its type annotation is updated to Union[int, None].

[codecov-commenter]

Codecov Report

Merging #2093 (ab0b2a7) into master (20e4b87) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2093      +/-   ##
==========================================
- Coverage   91.22%   91.22%   -0.01%     
==========================================
  Files         100      100              
  Lines       21486    21486              
==========================================
- Hits        19601    19600       -1     
- Misses       1885     1886       +1     

Impacted Files	Coverage Δ
redis/commands/core.py	82.85% <ø> (ø)
redis/asyncio/connection.py	82.75% <0.00%> (-0.12%)	⬇️

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[chayim]

Awesome, thank you @richli !