Remove only instance of :lineno:. It's ugly, and sphinx-lite won't bother to support it.

Signed-off-by: kay <kay.kim@10gen.com>

Author: i80and

source/core/master-slave.txt

@@ -67,7 +67,6 @@ specifying the master instance, as in the following
 operation in the :program:`mongo` shell:
 
 .. code-block:: javascript
-   :linenos:
 
    use local
    db.sources.find()