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/navigation/runtime/ktx/build.gradle b/navigation/runtime/ktx/build.gradle
index 6e5eb74..4cfa072 100644
--- a/navigation/runtime/ktx/build.gradle
+++ b/navigation/runtime/ktx/build.gradle
@@ -20,7 +20,8 @@
 import androidx.build.AndroidXExtension
 
 plugins {
-    id("SupportAndroidLibraryPlugin")
+    id("AndroidXPlugin")
+    id("com.android.library")
     id("org.jetbrains.kotlin.android")
 }