fixed commandline class reference

Author: chrisgorgo

doc/devel/cmd_interface_devel.rst

@@ -80,7 +80,7 @@ symbols. For an input defined in InputSpec to be included into the executed
 commandline ``argstr`` has to be included. Additionally inside the main
 interface class you need to specify the name of the executable by assigning it
 to the ``_cmd`` field. Also the main interface class needs to inherit from
-`CommandLine`_:
+:class:`nipype.interfaces.base.CommandLine`:
 
 .. testcode::