Colours: Open Appearance directly for >=22.04

[lah7]

Ubuntu MATE 22.04 now gets its colours via the Yaru project, but the old screen remains for backwards compatibility.

For context:

• https://discord.com/channels/712850672223125565/810848412815720448/955861079962058842
• https://discord.com/channels/712850672223125565/775655177188933652/951552821642268752