Commit
2194146d94600aff8dc165b9161f14346d00f878
by Oliver Smithjobs/osmocom-obs-sync: remove Ubuntu 20.04
We build binary packages for the last 2 LTS versions of Ubuntu, so
remove 20.04.
Related: https://osmocom.org/projects/cellular-infrastructure/wiki/Linux_Distributions
Change-Id: Ia93b272447032eb5224d8e14a75801dda8a596a8