GitHub actions documentation building for master indicates untagged

[klauer]

While untagged is accurate, master version number in built docs is less than ideal: 0+untagged.1.g8344678:

https://caproto.github.io/caproto/master/iocs.html

I think git fetch --tags && git describe with versioneer should have solved this (as in .ci/install.sh), so it'll require a bit of digging to figure out the details.