Upgrade GitLab chart to 3.3.3, prepare for Puma

Upgrades our version of the CN chart to 3.3.3, and prepares for the CN chart's move from 'unicorn' to 'webservice' as it replaces Unicorn under the hood with Puma.

Currently we handle the transition by replicating the tlsSecret logic between unicorn and webservice, so this can work with the master version of the chart when we upgrade. When we have fully upgraded, we can delete the old 'unicorn' entries.

Requires the matching helm-gitlab-config MR.