Delete SupportAndroidLibraryPlugin

Move the last bits of functionality to AndroidXPlugin.
Delete SupportAndroidLibraryPlugin.
We are down to a single plugin!!!

Test: ./gradelw assembleDebug
Change-Id: I76eb5e09b393424410bd612aab79c317f0473025
diff --git a/dumb-tests/build.gradle b/dumb-tests/build.gradle
index 0a29cc5..c541388 100644
--- a/dumb-tests/build.gradle
+++ b/dumb-tests/build.gradle
@@ -17,7 +17,8 @@
 import static androidx.build.dependencies.DependenciesKt.*
 
 plugins {
-    id("SupportAndroidLibraryPlugin")
+    id("AndroidXPlugin")
+    id("com.android.library")
 }
 
 dependencies {