Address code review

Author: ehsannas

firestore/testapp/README.md

@@ -13,10 +13,11 @@ The testapp performs the following:
 -   Gets a pointer to firebase::Auth, and signs in anonymously. This allows the
     testapp to access a Firebase Firestore instance with authentication rules
     enabled.
--   Initializes a Firestore instance, and sets its logging level to
+-   Initializes a Firestore instance and sets its logging level to
     `kLogLevelDebug` in order to see debug messages in the logs.
--   Tests that it can create Timestamp, SnapshotMetadata, and GeoPoint objects.
--   Creates a collection, and a document inside that collection.
+-   Tests that it can create `Timestamp`, `SnapshotMetadata`, and `GeoPoint`
+    objects.
+-   Creates a collection and a document inside that collection.
 -   Writes initial data to the document (`Set`), updates the document content
     (`Update`), reads the document back (`Get`), and checks that the contents
     match our expectation.