update actions as well

.github/workflows/build.yml

@@ -10,12 +10,12 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Setup Java JDK
-      uses: actions/setup-java@v3.9.0
+      uses: actions/setup-java@v4
       with:
-        java-version: 19
+        java-version: 21
         distribution: temurin
         cache: gradle