Deprecate properties w_xaxis, w_yaxis, and w_zaxis

[oscargus]

PR Summary

Originally deprecated in #11387.

PR Checklist

Tests and Styling

• [N/A] Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

• [N/A] New features are documented, with examples if plot related.
• [N/A] New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
• [N/A] Documentation is sphinx and numpydoc compliant (the docs should build without error).

[QuLogic]

@timhoffm suggested removal in 4.0; not sure if that's still the suggested time frame.

[oscargus]

Yeah, I noted that when digging up the original PR. Will change accordingly once a timeline is determined.

(Have sorted out the doc issue locally, but no point to trigger another CI before knowing the version.)