fix small typo in comment

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@63614 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/core/layerlist.py

@@ -246,7 +246,7 @@ class Layer(object):
     def SetMapType(self, mapType):
         """Sets map type of the layer.
 
-        :param mapType: can be 'raster', 'vector', 'rast3'
+        :param mapType: can be 'raster', 'vector', 'raster_3d'
         """
         if mapType not in self._mapTypes:
             raise ValueError("Wrong map type used: {mtype}".format(mtype=mapType))