Remove rootless docker build step

[VioletHynes]

Description

This is failing community PRs, and it also seems to make sense to me to keep CE + Ent building the same way.

TODO only if you're a HashiCorp employee

• Backport Labels: If this fix needs to be backported, use the appropriate backport/ label that matches the desired release branch. Note that in the CE repo, the latest release branch will look like backport/x.x.x, but older release branches will be backport/ent/x.x.x+ent.
  • LTS: If this fixes a critical security vulnerability or severity 1 bug, it will also need to be backported to the current LTS versions of Vault. To ensure this, use all available enterprise labels.
• ENT Breakage: If this PR either 1) removes a public function OR 2) changes the signature
  of a public function, even if that change is in a CE file, double check that
  applying the patch for this PR to the ENT repo and running tests doesn't
  break any tests. Sometimes ENT only tests rely on public functions in CE
  files.
• Jira: If this change has an associated Jira, it's referenced either
  in the PR description, commit message, or branch name.
• RFC: If this change has an associated RFC, please link it in the description.
• ENT PR: If this change has an associated ENT PR, please link it in the
  description. Also, make sure the changelog is in this PR, not in your ENT PR.

[github-actions]

CI Results:
All Go tests succeeded! ✅

[github-actions]

Build Results:
All builds succeeded! ✅

[fairclothjm]

LGTM! Thanks @VioletHynes !

[ryancragun]

From my very quick reading of this, tests that want to exec in a rootless container will no longer be able to in CE CI (which matches Ent). I suppose that is fine if that is the current limitation we have with our runners, though I'm curious what impact this will have?

I'll throw my thumb on this to get the pipeline unblocked but we probably ought to have a follow-up task to investigate whether or not we can re-enable this in some fashion.