Fix compiler warning from menu.c

The patch fixes the compiler warning below

menu.c: In function 'restoreMenuRecurs':
menu.c:2450:47: warning: '%s' directive output may be truncated writing up to 510 bytes into a region of size between 509 and 1019 [-Wformat-truncation=]
 2450 |         snprintf(buffer, sizeof(buffer), "%s\\%s", path, menu->frame->title);
      |                                               ^~

The code is taking care of checking properly the string passed to the buffer,
so there is no issue, the change is just to make the compiler happy.

src/menu.c

@@ -2440,7 +2440,7 @@ static int restoreMenu(WScreen *scr, WMPropList *menu)
 static int restoreMenuRecurs(WScreen *scr, WMPropList *menus, WMenu *menu, const char *path)
 {
 	WMPropList *key, *entry;
-	char buffer[512];
+	char buffer[1024];
 	int i, x, y, res;
 	Bool lowered;