Run gate-{name}-docs on infra-publish-jobs

The gate-{name}-docs publishes a draft copy of the docs for reviewers.
Published draft documents clearly aren't needed for gate jobs, however
this test will ensure that the docs still build correctly when merged.

Change-Id: I454103b5d5262d4aaeb6671b79892be7993bb2a6
Merge "Run gate-{name}-docs on infra-publish-jobs"