Fix yaml in index.md file (#60484)

Co-authored-by: mc <42146119+mchammer01@users.noreply.github.com>

Author: sarahs

content/code-security/concepts/index.md

@@ -14,3 +14,4 @@ children:
   - supply-chain-security
   - /vulnerability-reporting-and-management
   - /security-at-scale
+---