trivial tweak to single field index

Author: kay-kim

source/core/index-single.txt

@@ -167,14 +167,3 @@ document:
 
 See :ref:`query-subdocuments` for more information regarding querying
 on subdocuments.
-
-The index on the ``metro`` field can also support the following query:
-
-.. code-block:: javascript
-
-   db.factories.find( { metro: { $gte : { city: "New York" } } } )
-
-This query returns the above document because ``{ city: "New York",
-state: "NY" }`` is greater than ``{ city: "New York" }``. The order of
-comparison is in ascending key order in the order that the keys occur
-in the :term:`BSON` document.