Move setting maven group directly to each build.gradle.

Test: ./gradlew buildOnServer
Change-Id: If83e8d3d4bb8c9dd260f65c3898b6f0fa8ffc524
diff --git a/customtabs/build.gradle b/customtabs/build.gradle
index 8c9ff7d..ade1bda 100644
--- a/customtabs/build.gradle
+++ b/customtabs/build.gradle
@@ -1,3 +1,5 @@
+import android.support.LibraryGroups
+
 plugins {
     id("SupportAndroidLibraryPlugin")
 }
@@ -24,6 +26,7 @@
 supportLibrary {
     name = "Android Support Custom Tabs"
     publish = true
+    mavenGroup = LibraryGroups.SUPPORT
     inceptionYear = "2015"
     description = "Android Support Custom Tabs"
     legacySourceLocation = true