fixed underline in template doc

doc/en/user/source/extensions/mapml/template.rst

@@ -64,7 +64,7 @@ This would result in a head section that would resemble:
     </head>
 
 GetMap MapML Head Stylesheet Templating
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 The MapML format includes a map-head element that includes map-link elements to link to other resources, including map style variants.  Additional map-link elements can be added to the map-head element by creating a ``mapml-head.ftl`` template in the GeoServer data directory in the directory for the layer we wish to append map-links to.  For example we could create the ``mapml-head.ftl`` file under ``workspaces/tiger/nyc/poly_landmarks_shapefile/poly_landmarks``: 
 
 .. code-block:: bash