fix: use safer repr in warning

[tlambert03]

I found an edge case when trying to connect to a slot, where that slot itself had a recursion error in its __repr__ method, where the entire connection failed with a recursion error in what should have been a simple warning when the slot was not weak-refable. This PR uses object.__repr__(object) instead of repr(object), just in case the object in question in un-reprable

[codspeed-hq]

CodSpeed Performance Report

Merging #353 will not alter performance

_{Comparing tlambert03:safe-repr (8cd3233) with main (f1ca61a)}

Summary

✅ 67 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (f1ca61a) to head (8cd3233).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #353   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           21        21           
  Lines         2115      2116    +1     
=========================================
+ Hits          2115      2116    +1     

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