fix spacing

Author: shuangela

source/reference/operator/aggregation/queryStats.txt

@@ -360,7 +360,7 @@ Each document in the output array contains the following fields:
        mebibytes (MiB) worth of documents. Subsequent batches have a maximum size of 16 MiB. ``batchSize`` can enforce a
        smaller limit than 16 MiB, but not a larger one. When set, the
        ``batchSize`` is the lesser of ``batchSize`` documents or 16 MiB worth of
-        documents.
+       documents.
 
    * - ``key.comment``
      - String