Obsolete python2-caribou and python3-caribou as well (#1568670)
Also bump caribou obsoletes versions so that the latest caribou in F28 is
covered. I'll also bump caribou release separately, so that it still gets
installed when explicitly requested (it's a dep of cinnamon), but correctly
removed/obsoleted from Workstation installs.
Sorry for the mess with the obsoletes here. This should have really been done
when it got retired in the first place and it's more difficutly to make this
work retroactively now.