Remove `release/` from Android.gitignore (#3162)

Having `release/` in an Android project gitignore means those apps which have different
build types files for `debug` and `release` will fall into this 
and all `release` related files will be never added or will be removed from
repository at some point.

Android.gitignore

@@ -13,7 +13,8 @@
 bin/
 gen/
 out/
-release/
+#  Uncomment the following line in case you need and you don't have the release build type files in your app
+# release/
 
 # Gradle files
 .gradle/