PR Summary

After I closed #25673 because the root cause of that issue is in IPython mapping "qt" to "qt5agg", I realized that perhaps we could still do better about our error message.
While this change would not have actually resolved the question of "what is asking this to be qt5??", it would have at least not also raised the question of "why is qt6 not working? It is installed."

>>> plt.switch_backend("qtagg")
Traceback (most recent call last):
...
ImportError: Failed to import any of the following Qt binding modules: PyQt6, PySide6, PyQt5, PySide2
>>> plt.switch_backend("qt5agg")
Traceback (most recent call last):
...
ImportError: Failed to import any of the following Qt binding modules: PyQt5, PySide2

Now only outputs the bindings which were actually tested, rather than all 4 regardless of whether only qt5 bindings were tested.

PR Checklist

Linked Issue

• [N/A] Added "closes #0000" in the PR description to link it to the original issue.

Documentation and Tests

• [N/A] Has pytest style unit tests (and pytest passes)
• [N/A] Documentation is sphinx and numpydoc compliant (the docs should build without error).
• [N/A] New plotting related features are documented with examples.

Release Notes

• [N/A] New features are marked with a .. versionadded:: directive in the docstring and documented in doc/users/next_whats_new/
• [N/A] API changes are marked with a .. versionchanged:: directive in the docstring and documented in doc/api/next_api_changes/
• [N/A] Release notes conform with instructions in next_whats_new/README.rst or next_api_changes/README.rst