[Freedombox-pkg-team] plinth is marked for autoremoval from testing

[Debian testing autoremoval watch]

plinth 20.12 is marked for autoremoval from testing on 2020-08-04

It (build-)depends on packages with these RC bugs:
963369: python-testfixtures: FTBFS: dh_auto_test: error: pybuild --test -i python{version} -p 3.8 returned exit code 13