call useMetrics hook to check FxA profile metricsEnabled

[groovecoder]

How to test:

1. Since our local apps cannot receive webhook events from FXA, use the admin UI to update the SocialAccount for a user: In their "Extra data" field, edit the JSON to set "metricsEnabled": false
2. Open the Network developer tool in a browser window
3. Sign the user out and back into the app to make sure the front-end code has "fresh" profile data
   • [ ] On the resulting page, check the Network developer tool: there should be 0 requests to google-analytics or googletagmanager
4. Repeat step 1 but edit the JSON to set "metricsEnabled": true
5. Refresh the page
   • [ ] On the resulting page, check the Network developer tool: there should be 1+ requests to google-analytics or googletagmanager

• [x] ~l10n changes have been submitted to the l10n repository, if any.~
• [ ] I've added a unit test to test for potential regressions of this bug.
• [ ] I've added or updated relevant docs in the docs/ directory.
• [x] ~All UI revisions follow the coding standards, and use Protocol tokens where applicable (see /frontend/src/styles/tokens.scss).~
• [x] ~Commits in this PR are minimal and have descriptive commit messages.~