Dashboard: add trailing period to On this day reminder help text

[alshakero]

Proposed Changes

• Add a trailing period to the "On this day" toggle help text in the Notifications → Extras screen: "Reminders about your posts from past years."
• Update the corresponding unit test assertion to match.

Why are these changes being made?

• The help text was missing a terminating period, unlike the surrounding help copy on the screen. This is a small copy consistency fix.

Testing Instructions

• Run yarn test-client client/dashboard/me/notifications-extras.
• In the dashboard, go to Notifications → Extras and confirm the "On this day" toggle help text ends with a period.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• For UI changes, have you tested the affected components in dark mode?
• Have you tested accessibility for your changes? Ensure the feature remains usable with various user agents (e.g., browsers), interfaces (e.g., keyboard navigation), and assistive technologies (e.g., screen readers) (PCYsg-S3g-p2).
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
  • For UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-187487

Jetpack Cloud Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-187487&env=jetpack

Automattic for Agencies Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-187487&env=a8c-for-agencies

Dashboard Live (dotcom) (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-187487&env=dashboard

Dashboard Live (A4A) (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-187487&env=dashboard-a4a

[a8ci18n]

Translation for this Pull Request has now been finished.

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.