Don't save mathCAT settings to yaml (#19637)
Follow-up to #18323, #19373 and #19613
### Summary of the issue:
Since the introduction of MathCAT into NVDA in #18323, NVDA has
persisted MathCAT settings to a YAML file . This is at odds with current
project configuration standards, which use either configobj ini files,
or JSON. This also duplicates settings, as they're also saved to
`nvda.ini`.
Originally, these were stored in `%AppData%\MathCAT\prefs.yaml`, but as
of #19373, they are saved to `mathcat.yaml` in NVDA's config directory.
In neither case was `shouldWriteToDisk` checked before saving the
preferences. Additionaly, [NV Access's Corporate & Government
page](https://www.nvaccess.org/corporate-government/) states "To prevent
NVDA users from modifying their configuration or add-ons directly, user
write access to [`%APPDATA%\nvda`] must also be restricted". If
implemented, this would have stopped users from changing their MathCAT
settings in memory, as they had to be saved to YAML to be loaded by
MathCAT.
In #19613, the logic was changed to programmatically apply these
settings with `libmathcat.SetPreference`, which should solve the problem
of users without write access to their NVDA config directory being able
to change their MathCAT preferences. However, the code that wrote the
settings to the YAML file was not removed, nor did it contain any error
handling.
### Description of user facing changes:
None, but may avoid some errors in the logs.
### Description of developer facing changes:
Pyyaml is no-longer a dependency.
`mathPres.MathCAT.preferences.MathCATUserPreferences.save` has been
renamed to `apply`, and no longer saves the settings to YAML. Settings
persistance is handled by NVDA's configuration system.
### Description of development approach:
Removed the code that wrote MathCAT preferences to YAML, and any code
that only it depended on. Renamed `save` to `apply` using VS Code's
refactoring tool. Searched the repo for `yaml` and after confirming that
we don't rely on `pyyaml` anywhere else, ran `uv remove pyyaml`.
### Testing strategy:
Tested by loading the [Wikipedia page on the quadratic
formula](https://en.wikipedia.org/wiki/Quadratic_formula) in firefox.
Located some math and read it. Changed settings one at a time and tested
that they were applied correctly. Restarted NVDA and ensured that the
new settings were still present.
### Known issues with pull request:
None known
