menu: remove winbar code

No unmerged Vim patch, applicable to Neovim, depend on WinBar feature.
It was merged only for merging Vim patches.
It is currently useless in Neovim.
Remove it to avoid rendering issues.

Close https://github.com/neovim/neovim/issues/12689

src/nvim/normal.c

@@ -2601,11 +2601,6 @@ do_mouse (
                              oap == NULL ? NULL : &(oap->inclusive),
                              which_button);
 
-  // A click in the window toolbar has no side effects.
-  if (jump_flags & MOUSE_WINBAR) {
-    return false;
-  }
-
   moved = (jump_flags & CURSOR_MOVED);
   in_status_line = (jump_flags & IN_STATUS_LINE);
   in_sep_line = (jump_flags & IN_SEP_LINE);