Replace clear_connect_callbacks with _deregister_connect_callback

[dvora-h]

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Description of change

This change seems to have been missed in #2870 (@kristjanvalur)

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (ded9f7c) 91.36% compared to head (a153c80) 91.36%.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2955   +/-   ##
=======================================
  Coverage   91.36%   91.36%           
=======================================
  Files         126      126           
  Lines       32603    32603           
=======================================
+ Hits        29787    29789    +2     
+ Misses       2816     2814    -2     

Files Changed	Coverage Δ
redis/asyncio/client.py	91.98% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[chayim]

CI...

[kristjanvalur]

How did that happen?

[kristjanvalur]

Ah, it is in a __del__ handler. In fact, this code is not required and the __del__ handler can be removed, since the callbacks are weak andyway, the reason being to precisely not need __del__.
But I did grep for the function, so my bad on that.