Add deploymentAnnotations to external gateway

What does this MR do and why?

Adds deploymentAnnotations that are defined as empty by default but can be overridden in the main chart.

        deploymentAnnotations:
          secret.reloader.stakater.com/reload: some-cert

Also disables ctags by setting the CTAGS_COMMAND environment variable script to empty because releasing a new version of the indexer would break with the current ctag config. Original issue for ctags: Zoekt indexer doesn't use universal-ctags (gitlab-org/gitlab#431343 - closed).