Fix typo in documentation

doc/userdoc.org

@@ -2689,9 +2689,9 @@ actually stored in the ~checkpoint.h5~ file, the script is not a command
 line argument.
 
 By now, it is not possible to *simply* modify the script while
-resuming. This is done in purpose since it remains unclear if such a
-dangerous functionality should be make easy. Indeed allowing
-script modifications may lead to undefined behaviors.
+resuming. This is done on purpose since it remains unclear if such a
+dangerous functionality should be make easy. Indeed allowing script
+modifications may lead to undefined behaviors.
 #+END_note
 
 #+BEGIN_warning