Remove dependencies on Boost.StaticAssert

[Lastique]

Boost.StaticAssert has been merged into Boost.Config, so remove the dependency.

[pdimov]

I'm going to merge this, because otherwise

error: Unable to find file or target named
error:     '/boost/static_assert//boost_static_assert'
error: referred to from project at
error:     '/home/runner/work/boost_install/boost-root/libs/regex'
error: could not resolve project reference '/boost/static_assert'

as static_assert is no longer implicitly installed by depinst because boost/static_assert.hpp is in Config now.