Fixes Redis.from_url() return type

[davemcphee]

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Description of change

Fixes return type of Redis.from_url() (was None, now "Redis")

fixes #2971

[codecov-commenter]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (787d731) 91.37% compared to head (5138805) 66.57%.

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Additional details and impacted files

@@             Coverage Diff             @@
##           master    #2994       +/-   ##
===========================================
- Coverage   91.37%   66.57%   -24.81%     
===========================================
  Files         126      126               
  Lines       32608    32608               
===========================================
- Hits        29797    21710     -8087     
- Misses       2811    10898     +8087     

Files	Coverage Δ
redis/client.py	65.50% <100.00%> (-26.48%)	⬇️

... and 81 files with indirect coverage changes

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[dvora-h]

Fixed in #2963

[rafales]

Why not type it as Self which works better with subclasses? I see that typing_extensions is in dependencies, so it can be used to support pre 3.11 versions of python.