pgrade workflow to version 21.

Author: zzhlogin

.github/workflows/pr-build.yml

@@ -58,7 +58,7 @@ jobs:
 
       - uses: actions/setup-java@v4
         with:
-          java-version: 17
+          java-version: 21
           distribution: temurin
 
       - uses: gradle/wrapper-validation-action@v1