CI: upgrade java to 21

Author: SIMULATAN

.github/workflows/dev_build.yml

@@ -8,7 +8,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-java@v2
         with:
-          java-version: 17
+          java-version: 21
           distribution: adopt
       - name: Get Version
         id: get_version

.github/workflows/pull_request.yml

@@ -8,7 +8,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-java@v2
         with:
-          java-version: 17
+          java-version: 21
           distribution: adopt
       - name: Build
         run: ./gradlew build