Update .gitignore to exclude GoogleService-Info.plist for MLModelDownloader. (#7063)

* Restores ML Pods after M77.

* Fix Package.swift

* Update .gitignore to exclude GoogleService-Info.plist for MLModelDownloader.

Author: manjanac

.gitignore

@@ -32,6 +32,9 @@ FirebaseStorageSwift/Tests/Integration/Credentials.swift
 # FirebaseSegmentation integration tests GoogleService-Info.plist
 FirebaseSegmentation/Tests/Sample/GoogleService-Info.plist
 
+# FirebaseMLModelDownloader integration tests GoogleService-Info.plist
+FirebaseMLModelDownloader/Tests/Integration/Resources/GoogleService-Info.plist
+
 Secrets.tar
 
 # OS X