xdg-shell: remove constraint on popup parents

[Drew DeVault]

Bumping this patch for review.

>It seems that this was partially done in
>a3cf97ff982638bf7ed23b4303eba280c521b54d; this patch just corrects an
>oversight.
>---
> stable/xdg-shell/xdg-shell.xml | 3 ---
> 1 file changed, 3 deletions(-)
>
>diff --git a/stable/xdg-shell/xdg-shell.xml b/stable/xdg-shell/xdg-shell.xml
>index d524ea9..2255d77 100644
>--- a/stable/xdg-shell/xdg-shell.xml
>+++ b/stable/xdg-shell/xdg-shell.xml
>@@ -1007,9 +1007,6 @@
>       surface of their own is clicked should dismiss the popup using the destroy
>       request.
> 
>-      The parent surface must have either the xdg_toplevel or xdg_popup surface
>-      role.
>-
>       A newly created xdg_popup will be stacked on top of all previously created
>       xdg_popup surfaces associated with the same xdg_toplevel.
>