Mark publishing-api as using the default buildProject script
Mark publishing-api as using the default buildProject script

We changed publishing-api to use the default buildProject jenkins
script (see [publishing-api#1065](alphagov/publishing-api#1065)
and so our jenkins job no longer needs to explicitly wait on it before
reporting back to github.

alphagov/govuk-content-schemas,alphagov/govuk-content-schemas