Add blank line (GoogleCloudPlatform#1215)

Fixes b/68814312

Author: samtstern

firestore/src/main/java/com/example/firestore/snippets/ManageDataSnippets.java

@@ -404,6 +404,7 @@ void writeBatch() throws Exception {
     // [START fs_write_batch]
     // Get a new write batch
     WriteBatch batch = db.batch();
+
     // Set the value of 'NYC'
     DocumentReference nycRef = db.collection("cities").document("NYC");
     batch.set(nycRef, new City());