Rename pluginz to plugin in version catalog

Plugin was a reserved keyword when version catalogs launched and it
is no longer one, we can use these names now.

Also deletes a couple of unused version catalog entries

Test: ./gradlew bOS --dry-run
Change-Id: I90916b36f47332f86a97e0023511adc5b5474fbc
diff --git a/stableaidl/stableaidl-gradle-plugin/build.gradle b/stableaidl/stableaidl-gradle-plugin/build.gradle
index a0c775c..5aea267 100644
--- a/stableaidl/stableaidl-gradle-plugin/build.gradle
+++ b/stableaidl/stableaidl-gradle-plugin/build.gradle
@@ -54,9 +54,9 @@
     implementation(libs.apacheAnt)
     implementation(libs.kotlinStdlib)
 
-    testPlugin(libs.androidGradlePluginz)
+    testPlugin(libs.androidGradlePlugin)
 
-    testImplementation(libs.androidGradlePluginz)
+    testImplementation(libs.androidGradlePlugin)
     testImplementation(gradleTestKit())
     testImplementation(project(":internal-testutils-gradle-plugin"))
     testImplementation(libs.androidToolsAnalyticsProtos)