chore(getting-started): removes unneeded sections
chore(getting-started): removes unneeded sections

removes What's Included section and Styleguide section. Information about the styleguide is still in intro.

[#97135788]

sjolicoeur/pivotal-ui,npm/pivotal-ui,pivotal-cf/pivotal-ui,sjolicoeur/pivotal-ui,pivotal-cf/pivotal-ui,npm/pivotal-ui,sjolicoeur/pivotal-ui,npm/pivotal-ui,sjolicoeur/pivotal-ui,pivotal-cf/pivotal-ui,CanopyCloud/pivotal-ui,CanopyCloud/pivotal-ui,CanopyCloud/pivotal-ui