Fix documentation

Author: vferat

nipype/interfaces/mne/base.py

@@ -100,7 +100,7 @@ class WatershedBEM(FSCommand):
     >>> bem.inputs.subject_id = 'subj1'
     >>> bem.inputs.subjects_dir = '.'
     >>> bem.cmdline
-    'mne_watershed_bem --overwrite --subject subj1 --volume T1'
+    'mne watershed_bem --overwrite --subject subj1 --volume T1'
     >>> bem.run() 				# doctest: +SKIP
 
    """