After dropping the allow list we can also clean up the block list a bit.

Some candidates:

• https://searchfox.org/mozilla-central/source/widget/gtk/GfxInfo.cpp#698-702 (bug 1708682, turned out to be a dup of bug 1710400) done
• https://searchfox.org/mozilla-central/source/widget/gtk/GfxInfo.cpp#746-753 (needs revisiting, might be fixed by now, see bug 1673939 comment 29)
• https://searchfox.org/mozilla-central/source/widget/gtk/GfxInfo.cpp#656-662 (just bump the baseline to the Mesa version used in the oldest distro we still support so we can phase out block entries over time. Right now that's AFAIK RHEL 7 and Ubuntu 14.04 - and duh, they might be on Mesa 10 still)

I'm not planning to work on this atm and the info above is somewhat outdated by now, so closing.