fix(build): disable publishing to 8.0 Linux repos for now (#2032)

Our build scripts try to publish to all available combinations of Linux
repositories. It seems that, for now, barque has started forbidding
the implicit creation of repositories that way; for example, the publishing
steps for 2.2.8 failed because we cannot publish to the Debian 10 repo
for the 8.0 server release line (which does not support Debian 10).

For now, let's disable these repos to unblock the release, and follow
up with a ticket to re-enable the exact subset of repos that we can
and should publish to.

Author: addaleax