Update SECURITY.md: remove maintainer note, add trailing newline

Author: abcgco

SECURITY.md

@@ -8,6 +8,4 @@ responsibly through **GitHub Private Vulnerability Reporting (PVR)**.
 **To report**: Go to the [Security Advisories page](../../security/advisories/new)
 and submit a new advisory.
 
-**To enable PVR** (maintainers): Settings → Code security → Private vulnerability reporting → Enable.
-
-Please **do not** open public issues for security vulnerabilities.
+Please **do not** open public issues for security vulnerabilities.