feedback: make sure that a later message can overwrite a short warning

This fixes https://savannah.gnu.org/bugs/?57901.

Bug existed since version 3.0, commit 25e98776.

src/winio.c

@@ -2276,6 +2276,7 @@ void warn_and_shortly_pause(const char *msg)
 {
 	blank_bottombars();
 	statusline(ALERT, msg);
+	lastmessage = HUSH;
 	napms(1500);
 }