x11/cinnamon: fix screen recording function

Screen recording relies on gstreamer's vpx in particular.
If it's missing the error like this appear in ~/.xsession-errors

• (cinnamon:71729): WARNING **: 21:12:21.414: CinnamonRecorder: failed to parse pipeline: no element "vp8enc"

So add vpx plugin as a dependency to make it work.

PR: 288249