Build: stop installing Boost.Regex on Ubuntu
Build: stop installing Boost.Regex on Ubuntu

This is no longer needed.

nickhutchinson/benchmark,nickhutchinson/benchmark-cxx03,nickhutchinson/benchmark-cxx03,nickhutchinson/benchmark,nickhutchinson/benchmark,nickhutchinson/benchmark-cxx03,nickhutchinson/benchmark-cxx03,nickhutchinson/benchmark