Do not publish Android tests inside the NPM package

Summary:
We don't want to include tests as they're not valuable for our users + the might break users build if they try to run `./gradlew build`.

Changelog:
[Internal] [Changed] - Do not publish Android tests inside the NPM package

Reviewed By: cipolleschi

Differential Revision: D36600831

fbshipit-source-id: b88ee4dc93f276cd0729a2193346f5fcde34323c

ReactAndroid/.npmignore

@@ -5,3 +5,6 @@ build/
 .cxx/
 # Exclude buck config/jars for third-party libraries
 src/main/third-party/
+# Exclude Android & JVM tests
+src/test/
+src/androidTest/