DOCSP-36128 updating lookup performance (#6139) (#6254)

* DOCSP-36128 updating lookup performance

* DOCSP-36128 updating lookup performance

Author: ltran-mdb2

source/reference/operator/aggregation/lookup.txt

@@ -341,11 +341,11 @@ different ``$lookup`` operations.
 
    * - :ref:`Uncorrelated Subqueries <lookup-uncorrelated-subquery>`
 
-     - .. _uncorrelated-subqueries-performance: 
-
+     - .. _uncorrelated-subqueries-performance:
+     
        - ``$lookup`` operations that contain uncorrelated subqueries
-         typically perform better when the inner pipeline can reference
-         an index on the ``foreignField``. 
+         perform better when the inner pipeline can reference an
+         index of the foreign collection.
 
        - MongoDB only needs to run the ``$lookup`` subquery once before
          caching the query because there is no relationship between the