Scope change & typo in /support/security - Mailing list pgsql-www

The first attached patch fixes grammar in /support/security.  The second adds
PostgreSQL Anonymizer to the CNA scope.  cna@postgresql.org decided on that
scope addition in 2024-03 and issued multiple CVEs[1] on the basis of that
decision, but I missed updating the page.

[1]
https://www.cve.org/CVERecord?id=CVE-2024-2338
https://www.cve.org/CVERecord?id=CVE-2024-2339
https://www.cve.org/CVERecord?id=CVE-2025-5690