Deleting a snippet of dead code -- the MGOTODIR menu doesn't have any

Deleting a snippet of dead code -- the MGOTODIR menu doesn't have any
functions that could be executed -- other than the line-edition ones,
which are executed under do_prompt().  So the latter won't return
unless either it was cancelled or an answer was given.  Also, if it
/had/ returned with a value bigger than zero, it tried to put back
the key sequence for do_gotolinecolumn_void(), which does not exist
in the MBROWSER menu, so this would not have done anything.

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@5744 35c25a1d-7b9e-4130-9fde-d3aeb78583b8