Remove extra (#1709)

Author: schmidt-sebastian

packages/firestore/test/integration/util/helpers.ts

@@ -195,7 +195,7 @@ export function withTestDbsSettings(
       'test-app-' + appCount++
     );
 
-    const firestore = firebase.firestore!!(app);
+    const firestore = firebase.firestore!(app);
     firestore.settings(settings);
 
     let ready: Promise<firestore.FirebaseFirestore>;