update github build to java 16

.github/workflows/package.yaml

@@ -12,16 +12,11 @@ jobs:
       - uses: actions/checkout@v2
         with:
           submodules: true
-      - name: Set up JDK 15.0.2
-        if: ${{ runner.os == 'Linux' }}
-        uses: joschi/setup-jdk@v2
-        with:
-          java-version: 15
-      - name: Set up JDK 14.0.2
-        if: ${{ runner.os == 'Windows' }}
-        uses: actions/setup-java@v1
+      - name: Set up JDK 16.0.1
+        uses: actions/setup-java@v2
         with:
-          java-version: 14.0.2
+          distribution: 'adopt'
+          java-version: '16.0.1'
       - name: Show Build Versions
         run: ./gradlew -v
       - name: Cache Gradle packages