Switch version scheme to release-branch-semver.

[QuLogic]

PR Summary

While setuptools-scm does not yet support our branch naming scheme for release branches, it will soon [1]. And we won't have to worry about that until we actually branch for 3.5.0, since the v3.4.x branch doesn't use it.

[1] pypa/setuptools_scm#573

Fixes #19419.

PR Checklist

• [n/a] Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (run flake8 on changed files to check).
• [n/a] New features are documented, with examples if plot related.
• [n/a] Documentation is sphinx and numpydoc compliant (the docs should build without error).
• Conforms to Matplotlib style conventions (install flake8-docstrings and run flake8 --docstring-convention=all).
• [n/a] New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• [n/a] API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).

[tacaswell]

From the logs:

Successfully installed matplotlib-3.5.0.dev984+g483e21154