Add back dependency for FirebaseFirestoreInternal

IntegrationTesting/ClientApp/Podfile

@@ -25,6 +25,7 @@ target 'ClientApp-CocoaPods' do
   pod 'FirebaseDatabase', :path => '../../'
   pod 'FirebaseDatabaseSwift', :path => '../../'
   pod 'FirebaseDynamicLinks', :path => '../../'
+  pod 'FirebaseFirestoreInternal', :path => '../../'
   pod 'FirebaseFirestore', :path => '../../'
   pod 'FirebaseFirestoreSwift', :path => '../../'
   pod 'FirebaseFunctions', :path => '../../'