Running the Dockerfiles in CI seemed like a good idea, but I'd forgotten that
they pull from the master branch, rather than using local source. Could be
reinstated if we make Dockerfiles use local source as discussed in trac#5574.
This reverts commit 712728c331ea3518b1964bbc7fcf06ff2c567064.
This allows us to use an identical build in CI and in local development. Not the
most optimal for CI, but means less to maintain and no inconsistencies.
Previously had partial docs for Fedora 31. This updates to Fedora 33, adds
support for audio and video and adds dependencies to allow the test suite to run
to completion.
