Fix CopyGoogleServicesPlugin for dataconnect

A recent change to `CopyGoogleServicesPlugin.kt` in #7454 caused it to skip all of its logic if the project already had its own `google-services.json` (as firebase-dataconnect _does_). Part of this logic is to apply the `com.google.gms.google-services` Gradle plugin when running (or compiling) tests. The `firebase-dataconnect` project relied on this side effect and the changes to `CopyGoogleServicesPlugin.kt` caused this side effect to no longer happen to firebase-dataconnect, causing the following build error:

```
firebase-dataconnect/src/androidTest/kotlin/com/google/firebase/dataconnect/testutil/FirebaseAppIdTestUtil.kt:23:68 Unresolved reference 'string'.
```

The fix in this commit modifies `CopyGoogleServicesPlugin.kt` to apply the `com.google.gms.google-services` Gradle plugin just as it did before, even if the project defines its own `google-services.json`. This was probably the intended behavior all along.

Author: dconeybe

plugins/src/main/java/com/google/firebase/gradle/plugins/CopyGoogleServicesPlugin.kt

@@ -17,7 +17,6 @@
 package com.google.firebase.gradle.plugins
 
 import com.android.build.gradle.BaseExtension
-import com.android.build.gradle.internal.tasks.factory.dependsOn
 import java.io.File
 import org.gradle.api.Plugin
 import org.gradle.api.Project
@@ -38,18 +37,17 @@ import org.gradle.kotlin.dsl.register
 abstract class CopyGoogleServicesPlugin : Plugin<Project> {
   override fun apply(project: Project) {
     if (File(project.projectDir, "google-services.json").exists()) {
-      project.logger.warn("Google Services file already present in project, skipping copy task")
-      return
-    }
-
-    val sourcePath = getSourcePath(project)
-    val copyRootGoogleServices = registerCopyRootGoogleServicesTask(project, sourcePath)
-
-    project.allprojects {
-      // fixes dependencies with gradle tasks that do not properly dependOn `preBuild`
-      tasks.configureEach {
-        if (name !== "copyRootGoogleServices") {
-          dependsOn(copyRootGoogleServices)
+      project.logger.info("Google Services file already present in project, skipping copy task")
+    } else {
+      val sourcePath = getSourcePath(project)
+      val copyRootGoogleServices = registerCopyRootGoogleServicesTask(project, sourcePath)
+
+      project.allprojects {
+        // fixes dependencies with gradle tasks that do not properly dependOn `preBuild`
+        tasks.configureEach {
+          if (name !== "copyRootGoogleServices") {
+            dependsOn(copyRootGoogleServices)
+          }
         }
       }
     }