python/apigen: Fix support for pybind11 overloaded functions

[jbms]

This was accidentally broken by
#357.

[codecov]

Codecov Report

Attention: Patch coverage is 96.55172% with 1 line in your changes missing coverage. Please review.

Project coverage is 77.87%. Comparing base (9ec088e) to head (dda690b).
Report is 10 commits behind head on main.

Files	Patch %	Lines
sphinx_immaterial/apidoc/python/apigen.py	96.55%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #378       +/-   ##
===========================================
+ Coverage   67.19%   77.87%   +10.67%     
===========================================
  Files          68       68               
  Lines        8515     8645      +130     
===========================================
+ Hits         5722     6732     +1010     
+ Misses       2793     1913      -880     

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[2bndy5]

Its odd that the added test for this uses a pure python. Is it safe to assume pybind11 will generate bindings the same way in the future?

[jbms]

Okay, I changed the test to use actual pybind11.