Use Java 21 in GitHub workflow

Author: PepperCode1

.github/workflows/build.yml

@@ -7,11 +7,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - name: Set up JDK 17
+      - name: Set up Java
         uses: actions/setup-java@v4
         with:
           distribution: temurin
-          java-version: 17
+          java-version: 21
           check-latest: true
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v5