Update Java version in Github workflow (#4052)

Summary:
Pull Request resolved: https://github.com/facebook/flipper/pull/4052

Update to use Java 11 instead of 1.8.

Aim is to bring parity with the other existing workflows but more importantly fix the build as is broken at the moment.

Reviewed By: antonk52

Differential Revision: D39254936

fbshipit-source-id: c60332a288d9a671df5db0180fb501ddf185a075

.github/workflows/react-native-example.yml

@@ -38,10 +38,10 @@ jobs:
     - uses: actions/setup-node@v2.1.5
       with:
         node-version: 14.x
-    - name: set up JDK 1.8
+    - name: set up JDK
       uses: actions/setup-java@v1
       with:
-        java-version: 1.8
+        java-version: 11
     - name: Compute build cache
       run: ${GITHUB_WORKSPACE}/scripts/checksum-android.sh checksum-android.txt
     - uses: actions/cache@v2