Move to AGP 3.0.0 stable 😁

Finally after many months of pain, suffering and tears we get to
move to the stable version of AGP even it this is going to last
us a short while until we need the next bleeding edge AGP feature
in support library to make our lives gloomy yet again.

For now - rejoice!

Test: ./gradlew buildOnServer
Change-Id: Ia6e1f7a8ecc4ecc4e79283d970d6defbd70828c6
diff --git a/buildSrc/dependencies.gradle b/buildSrc/dependencies.gradle
index cacfeff..ebeaa7e 100644
--- a/buildSrc/dependencies.gradle
+++ b/buildSrc/dependencies.gradle
@@ -32,7 +32,7 @@
     libs.gradle = 'com.android.tools.build:gradle:' + androidPluginVersionOverride
 } else {
     // Keep gradle plugin version in sync with ub_supportlib-master manifest.
-    libs.gradle = 'com.android.tools.build:gradle:3.0.0-beta7'
+    libs.gradle = 'com.android.tools.build:gradle:3.0.0'
 }
 
 //arch components