add region tag (#1427)

* add region tag

* Update app.yaml

Author: angelafunk

appengine-java11/http-server/src/main/appengine/app.yaml

@@ -12,5 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# [START gae_java11_runtime]
 runtime: java11
 # No need for an entrypoint with single fatjar with correct manifest class-path entry.
+# [END gae_java11_runtime]