libxml220 documentation is intentionally omitted, as it doesn't contain
anything usable from JavaScript.

These packages now seem to be dependencies of systemd-udev, which is a
restricted package that can't be removed. So, we shouldn't remove these
packages.

This GIR file is no longer exposed by gnome-shell, there's no more JS
code that uses it.

On the latest Fedora images, the Mutter libraries have bumped their API
versions.

Uninstalling gdm seems to make the build hang indefinitely. Let's not
uninstall it.

Fix Dockerfile

Fix the `-Ddoctool` option, which was changed to be a "feature" option instead of a boolean.

https://gitlab.gnome.org/GNOME/gobject-introspection/commit/efbd35d290d35e37994d441c9f2e4c0dffcd9cec

Dockerfile: fix gobject-introspection build

This is a large update which does the following:

 * update the mutter libs (meta, clutter, cogl, etc)
 * split the container into build and run time images
 * update the images and specify Fedora 31
 * use fedora-minimal for the run time image
 * use bundler's deployment option to install gems into /opt/devdocs

Dockerfile: bump and specify fedora image to 31, and fix locale

We don't want to scrape these ourselves (and also it stopped working
anyway for some reason); we'll download the pre-scraped docsets for
these from devdocs.

This should be even smaller than fedora-minimal, and also corresponds to
what devdocs already has in its Dockerfile-alpine.

We change the Ruby version to 2.6.5 to match what we build with in the
Fedora 31 image, and change the download step to download only the css
and javascript docsets.

Fix CSS/JavaScript docsets, smaller image

These are older mutter GIRs we can't install with dnf

Add mutter-3 and mutter-4 libs for older GNOME Shell compatibility

See: Infrastructure/Websites#280