Fix memory leak in win_create_muc()

I suspect this was just a copy paste error.
`_win_create_simple_layout()` is called in other creation functions like
`win_create_config()` or `win_create_private()`.

I suspect when `win_create_muc()` was created it was just copied. But in
this function we actually set the layout ourself later.

So calling the function isn't needed.

Regards https://github.com/profanity-im/profanity/issues/1279

src/ui/window.c

@@ -167,7 +167,6 @@ win_create_muc(const char *const roomjid)
     int cols = getmaxx(stdscr);
 
     new_win->window.type = WIN_MUC;
-    new_win->window.layout = _win_create_simple_layout();
     ProfLayoutSplit *layout = malloc(sizeof(ProfLayoutSplit));
     layout->base.type = LAYOUT_SPLIT;