Bump openjdk from 8 to 16

Bumps openjdk from 8 to 16.

---
updated-dependencies:
- dependency-name: openjdk
  dependency-type: direct:production
  update-type: version-update:semver-major
...
Signed-off-by: dependabot[bot] <support@github.com>

Dockerfile

@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM openjdk:8
+FROM openjdk:16
 
 RUN set -ex \
     && apt-get update \