use Java 11 for CI

Author: thestinger

.github/workflows/build.yml

@@ -11,9 +11,9 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
-      - name: Set up JDK 1.8
+      - name: Set up JDK 11
         uses: actions/setup-java@v1
         with:
-          java-version: 1.8
+          java-version: 11
       - name: Build with Gradle
         run: ./gradlew build