Fix comment

Author: tom-andersen

google-cloud-firestore/src/main/java/com/google/cloud/firestore/BulkWriter.java

@@ -161,7 +161,7 @@ enum OperationType {
   private final ScheduledExecutorService bulkWriterExecutor;
 
   /**
-   * The BulkWriter will shutdown executor when closed and are writes are done. This is important to
+   * The BulkWriter will shutdown executor when closed and all writes are done. This is important to
    * prevent leaking threads.
    */
   boolean autoShutdownBulkWriterExecutor;