* After https://github.com/mozilla/webservices-infra/pull/12034 landed, the current pages are no longer needed.
This commit:
* Removes the /legal/terms and /legal/privacy pages and their routes from fxa-settings and content-server.
* Removes the markdown rendering components and legal-docs fetch helper that existed only to serve those pages.
* Retires the legal-docs build pipeline (clone-legal-docs.sh, legal-prime) and the now-unread LEGAL_DOCS_URL config.
Closes #[PAY-3877](https://mozilla-hub.atlassian.net/browse/PAY-3877)