linter: make sure the shortcuts bar will redrawn when exiting early

The two help lines will be redrawn in main() only when the current
menu is not MMAIN.  So, set it to MLINTER as soon as the help lines
are cleared, just before preparing to invoke the linter.

This fixes https://savannah.gnu.org/bugs/?53967.
Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>

src/text.c

@@ -3116,6 +3116,7 @@ void do_linter(void)
 	}
 
 	blank_bottombars();
+	currmenu = MLINTER;
 	statusbar(_("Invoking linter, please wait"));
 
 	construct_argument_list(&lintargs, openfile->syntax->linter, openfile->filename);