Update source/core/read-operations.txt

Modified for better translation

Author: puentesarrin

source/core/read-operations.txt

@@ -48,7 +48,7 @@ syntax: [#formal-query-structure]_
   in the :program:`mongo` shell to list the current collections in the
   database.
 
-- Queries in MongoDB are :term:`BSON` objects that use using a set of
+- Queries in MongoDB are :term:`BSON` objects that use a set of
   :doc:`query operators </reference/operators>` to describe query
   parameters.