DOCS-9188: the $gt operator requires the $

Author: schmalliso

source/core/index-compound.txt

@@ -79,7 +79,7 @@ as well as both ``item`` and ``stock`` fields:
 .. code-block:: javascript
 
    db.products.find( { item: "Banana" } )
-   db.products.find( { item: "Banana", stock: { gt: 5 } } )
+   db.products.find( { item: "Banana", stock: { $gt: 5 } } )
 
 For details, see :ref:`compound-index-prefix`.