github: Build on JDK 21

Author: Juuxel

.github/workflows/gradle.yml

@@ -9,15 +9,16 @@ jobs:
       matrix:
         os: [ubuntu-latest, windows-latest]
         java: [
-          17 # Target
+          21 # Target
         ]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v2
-      - uses: gradle/wrapper-validation-action@v1
+      - uses: actions/checkout@v4
+      - uses: gradle/actions/wrapper-validation@v3
       - name: Set up JDK ${{ matrix.java }}
-        uses: actions/setup-java@v1
+        uses: actions/setup-java@v4
         with:
+          distribution: 'microsoft'
           java-version: ${{ matrix.java }}
       - name: Grant execute permission for gradlew
         if: ${{ runner.os != 'Windows' }}