Rename Monthly Monitor report to *Plus report

[Vinnl]

References:

Jira: MNTOR-3512
Figma: N/A

Description

Also, since that setting only applies to Plus users, moved the string to the non-localised strings. (The previous string might come back in a future feature, but as I understand it, Pontoon will remember it for easy re-translation.)

Screenshot (if applicable)

How to test

Visit the Settings page with a Plus account.

Checklist (Definition of Done)

• Localization strings (if needed) have been added.
• Commits in this PR are minimal and have descriptive commit messages.
• I've added or updated the relevant sections in readme and/or code comments
• I've added a unit test to test for potential regressions of this bug. - N/A, string change
• If this PR implements a feature flag or experimentation, the Ship Behind Feature Flag status in Jira has been set
• Product Owner accepted the User Story (demo of functionality completed) or waived the privilege.
• All acceptance criteria are met.
• Jira ticket has been updated (if needed) to match changes made during the development process.
• Jira ticket has been updated (if needed) with suggestions for QA when this PR is deployed to stage.

[github-actions]

Preview URL 🚀 : https://blurts-server-pr-4984-mgjlpikfea-uk.a.run.app

[github-actions]

Cleanup completed - database 'blurts-server-pr-4984' destroyed, cloud run service 'blurts-server-pr-4984' destroyed