Update GitHub Actions to use latest versions

Author: hypfvieh

.github/workflows/maven_jdk21.yml

@@ -15,9 +15,9 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Set up JDK 21
-      uses: actions/setup-java@v4
+      uses: actions/setup-java@v5
       with:
         java-version: '21'
         distribution: 'temurin'