Remove use of asyncio.coroutines.iscoroutinefunction()

[AlexWaygood]

Fixes #747.

If we land this, I'll cut a new rc release, out of an abundance of caution

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.26%. Comparing base (224f8d5) to head (2f3cdda).

@@           Coverage Diff           @@
##             main     #769   +/-   ##
=======================================
  Coverage   97.26%   97.26%           
=======================================
  Files           3        3           
  Lines        7862     7862           
=======================================
  Hits         7647     7647           
  Misses        215      215           

Flag	Coverage Δ
3.10	88.85% <100.00%> (ø)
3.10.4	88.85% <100.00%> (ø)
3.11	88.03% <100.00%> (ø)
3.11.0	87.28% <100.00%> (ø)
3.12	87.96% <50.00%> (-0.02%)	⬇️
3.12.0	87.95% <50.00%> (-0.02%)	⬇️
3.13	83.39% <0.00%> (ø)
3.13.0	84.09% <50.00%> (-0.02%)	⬇️
3.14	79.54% <0.00%> (ø)
3.9	89.54% <100.00%> (ø)
3.9.12	89.54% <100.00%> (ø)
pypy3.10	88.69% <100.00%> (ø)
pypy3.11	87.89% <100.00%> (ø)
pypy3.9	89.37% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/typing_extensions.py	94.00% <100.00%> (ø)

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[woutdenolf]

I'll cut a new rc release, out of an abundance of caution

Thanks good sir!

[AlexWaygood]

rc2 is out now, thanks for the report! https://pypi.org/project/typing-extensions/4.16.0rc2/