Update Java version from 17 to 21 in workflow

Author: chadlwilson

.github/workflows/pr_workflow.yml

@@ -18,7 +18,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@dded0888837ed1f317902acf8a20df0ad188d165 # v5.0.0
         with:
-          java-version: 17
+          java-version: 21
           distribution: temurin
       - name: Build with Gradle
         run: ./gradlew assemble check