fix spell mistake in text install

this bug appear on lenovo station.
	modified:   dialog/di_dialog.py

dialog/di_dialog.py

@@ -249,7 +249,7 @@ class MountPoint(Dialog):
                     ri_data.Partition.unit))
 
             exit_info,string=Dialog.dialog.menu(text="There are five columns in the mount point display frame.\n Device Mountpoint Filesystem Format Size",
-                                        height=self.height,width=self.width,menu_height=(len(list) > self.height and self.helght - 2 or len(list) ),
+                                        height=self.height,width=self.width,menu_height=(len(list) > self.height and self.height - 2 or len(list) ),
                                         choices=list,title='Mount',ok_label='edit',help_button=1,help_label='Next',clear=1)
             if exit_info == 0 :
                 # edit mountpoint