remove SmithyBuild (probably a leftover from a merge mistake)

[kubukoz]

          I think we should remove the `SmithyBuild` one (it's probably a leftover from a merge mistake). 

I think the reason is that we used to rely on the smithy-build pojo, but it was not flexible enough for what we needed to do. So we went straight-to-json I think. Better look at the history though

Originally posted by @Baccata in #1610 (comment)