Fix docs-lint `manifest unknown` error

The issue is:

WARNING: Failed to pull image with policy "always": Error response from daemon: manifest for
 registry.gitlab.com/gitlab-org/gitlab-docs/lint-html:alpine-3.15-ruby-3.0.3-cee62c13 not found: 
manifest unknown: manifest unknown (manager.go:203:0s)

ERROR: Job failed: \
failed to pull image "registry.gitlab.com/gitlab-org/gitlab-docs/lint-html:alpine-3.15-ruby-3.0.3-cee62c13" 
with specified policies [always]:disappointed: Error response from daemon: 
manifest for registry.gitlab.com/gitlab-org/gitlab-docs/lint-html:alpine-3.15-ruby-3.0.3-cee62c13 
not found: manifest unknown: manifest unknown (manager.go:203:0s)

It doesn't happen on our Ruby 3 MR !70798 (closed) likely because we don't update docs here, but happens on the experimental Ruby 3 MR which includes Arel-related changes including docs: !84940 (closed).

Failing job: https://gitlab.com/gitlab-org/gitlab/-/jobs/2326025342

It'll likely fail on Ruby 3 as well as soon it gets triggered (when any docs update will happen).

We need to check if the requested image does exist in our registry, and if not, create it.