speller: remove a pointless message -- it is never seen

When using the internal spell checker, the message gets overwritten
immediately by "Creating misspelled word list...", and when using
the external spell checker, nano immediately exits from curses mode
and thus the message disappears (when in a terminal emulator) or it
soon gets wiped by the spell checker (when on a Linux console), thus
creating a little flash on the bottom row, which we can do without.

src/text.c

@@ -2981,7 +2981,6 @@ void do_spell(void)
 	}
 
 	blank_bottombars();
-	statusbar(_("Invoking spell checker, please wait"));
 
 	spell_msg = (alt_speller != NULL) ? do_alt_speller(temp) :
 										do_int_speller(temp);