[Android] Fix "Minimum supported Gradle version is 4.1-milestone-1"

android/build.gradle

@@ -7,7 +7,7 @@ buildscript {
         maven { url 'https://maven.google.com' }
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.+'
+        classpath 'com.android.tools.build:gradle:3.0.0-alpha4'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files.