Disable Android tests on Appveyor (#25066)

Summary:
Android is failing on Appveyor. Removing to regain signal on Windows.

See https://ci.appveyor.com/project/Facebook/react-native/builds/24869333/job/tnif7yt4x0lfisju for an example.
Pull Request resolved: #25066

Differential Revision: D15532362

Pulled By: hramos

fbshipit-source-id: afb55297b385d8b7e497d9cf4d26420f9502df44

.appveyor/config.yml

@@ -38,7 +38,7 @@ build_script:
   - yarn run flow-check-android
   - yarn run flow-check-ios
   - yarn run test
-  - gradlew.bat RNTester:android:app:assembleRelease
+  # - gradlew.bat RNTester:android:app:assembleRelease
 
 cache:
   - node_modules