Update maven_repositories url (facebook#21056)

Summary:
Update maven_repositories url to `https://dl.google.com/dl/android/maven2/` while the previous url `https://maven.google.com` has always been redirect to `https://dl.google.com/dl/android/maven2/`.
Pull Request resolved: facebook#21056

Differential Revision: D9789079

Pulled By: hramos

fbshipit-source-id: 9907d46fe7356f5b710fa4a8b9a4b0903d732967

.buckconfig

@@ -7,7 +7,7 @@
 
 [maven_repositories]
   central = https://repo1.maven.org/maven2
-  google = https://maven.google.com
+  google = https://dl.google.com/dl/android/maven2/
 
 [alias]
   rntester = //RNTester/android/app:app