Use Java 21 to run Jenkins security scanner

Author: uhafner

.github/workflows/jenkins-security-scan.yml

@@ -17,5 +17,5 @@ jobs:
   security-scan:
     uses: jenkins-infra/jenkins-security-scan/.github/workflows/jenkins-security-scan.yaml@v2
     with:
-      java-cache: 'maven' # Optionally enable use of a build dependency cache. Specify 'maven' or 'gradle' as appropriate.
-      # java-version: 21 # Optionally specify what version of Java to set up for the build, or remove to use a recent default.
+      java-cache: 'maven'
+      java-version: 21