chore(release): use exec instead of git-gulp
chore(release): use exec instead of git-gulp

- git-gulp is buggy - and its streams don't return what they should

[#81140264]

Signed-off-by: Bebe Peng <cc70e5ee229c0d4b3ccc63a88c70622c84c389ff@pivotal.io>

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