Upgrade github CI workflow configuration.

Author: laurentg

.github/workflows/ci.yml

@@ -7,13 +7,13 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v2
-      - name: Set up JDK 11
-        uses: actions/setup-java@v1
+      - uses: actions/checkout@v4
+      - name: Set up JDK 20
+        uses: actions/setup-java@v4
         with:
-          java-version: 11
+          java-version: 20
       - name: Cache Gradle packages
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ~/.gradle/caches
           key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle') }}