Revert "ci: add xorgproto dep to Arch build"

This reverts commit 35bc3e662a.

Per [1], the dependency has been re-added and we shouldn't need to
explicitly install it anymore.

[1]: https://bugs.archlinux.org/task/64914

.builds/archlinux.yml

@@ -14,7 +14,6 @@ packages:
   - xcb-util-errors
   - xcb-util-image
   - xcb-util-wm
-  - xorgproto
 sources:
   - https://github.com/swaywm/wlroots
 tasks: