graphics/feh: Update to 3.1

Update graphics/feh to 3.1. This brings with it some changes and removes
some deprecated things, amongst those hte cam related scripts. Remove the
CAM option because of this, and adjust depdenencies.

See changelogs for further details:
https://feh.finalrewind.org/archive/3.0/
https://feh.finalrewind.org/archive/3.1/