Do not skip the client build in dockerized selenium tests

[nsoranzo]

This allows the removal of the docker run of make client-production-maps, which was run on a docker image for the
wrong version of node.

Alternative to #7278 with the advantage of not having to remember to sync the node version in 2 places.

[nsoranzo]

@galaxybot test py3

[dannon]

@mvdbeek @nsoranzo Argh, good catch -- thank you both. I was chasing a red herring looking at the chromedriver startup failures seen in the logs! I had completely forgotten that we set up this separate client-docker-build pipeline for selenium (we needed it in the days before Galaxy managed its own node/client stuff), and we do not need it anymore -- and it's best to test against the single pinned version specified in the galaxy common startup bit anyway.

[nsoranzo]

Same number of failed Selenium tests here and in #7278, should be good to go.

[dannon]

@nsoranzo Yeah, that's what I was just looking at. Many of those pass locally for me, but this is a clear improvement and I can follow up looking into that separately. Going to go ahead and merge.