update toolchain to Java 16

.github/workflows/devbuild.yml

@@ -15,10 +15,10 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-    - name: Set up JDK 1.8
+    - name: Set up JDK 16
       uses: actions/setup-java@v1
       with:
-        java-version: 1.8
+        java-version: 16
     - name: Cache Gradle packages
       uses: actions/cache@v2
       with: