Closes #8745 Remove OneTimeFxaPushReset from FxaPushSupportFeature

[Stuie]

Removing the OneTimeFxaPushReset class, its usages, and unit tests.

No tests were added because no code was added.

The reference browser does not refer to the removed class, so there's no PR to address this change on that repository.

Pull Request checklist

• Quality: This PR builds and passes detekt/ktlint checks (A pre-push hook is recommended)
• Tests: This PR includes thorough tests or an explanation of why it does not
• Changelog: This PR includes a changelog entry or does not need one
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features

After merge

• Milestone: Make sure issues closed by this pull request are added to the milestone of the version currently in development.
• Breaking Changes: If this is a breaking change, please push a draft PR on Reference Browser to address the breaking issues.

[jonalmeida]

Lovely!

Not merging this immediately though as we're investigating some push-related bugs and it's better to have fewer moving parts in this domain for a few days.

[jonalmeida]

Note for self: this can be landed by the end of the week.

[mergify]

This pull request has conflicts when rebasing. Could you fix it @Stuie? 🙏