replace deprecated iscoroutinefunction with supported version

[jenshnielsen]

The async version was deprecated in 3.14 so replace it will the one from inspect that is available in all supported versions of python

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 59.89%. Comparing base (77b754d) to head (0b6cf48).
⚠️ Report is 26 commits behind head on main.

Files with missing lines	Patch %	Lines
src/qcodes/utils/function_helpers.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7753   +/-   ##
=======================================
  Coverage   59.89%   59.89%           
=======================================
  Files         352      352           
  Lines       31807    31806    -1     
=======================================
  Hits        19051    19051           
+ Misses      12756    12755    -1     

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