Update feature matrix section titles

Author: felickz

GHAS-on-GHES-feature-matrix.md

@@ -9,9 +9,9 @@ The following tables include notable feature releases for GitHub Advanced Securi
       - [Contents](#contents)
       - [How do I read this document?](#how-do-i-read-this-document)
   - [Release notes](#release-notes)
-  - [Secret scanning](#secret-scanning)
-  - [Code scanning](#code-scanning)
-  - [Supply-chain security](#supply-chain-security)
+  - [Secret Protection](#secret-protection)
+  - [Code Security](#code-security)
+      - [Code scanning](#code-scanning)
       - [Dependabot Alerts](#dependabot-alerts)
       - [Dependabot Updates](#dependabot-updates)
       - [Dependency Review and submission API](#dependency-review-and-submission-api)