editors/ad: update to 0.3.1

• x11/xclip can still be used by ad, but is now optional and only used when running under X11 (for Wayland, x11/wl-clipboard is used). Remove the dependency and add a note in pkg-message.

Changelog: https://github.com/sminez/ad/releases/tag/0.3.0
Changelog: https://github.com/sminez/ad/releases/tag/0.3.1