Fix link on end-to-end quick start guide doc

What does this MR do?

Backport of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14668.

I had opened this other MR before (https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/30665), but I had to close it due to some issues in the pipeline. This is why I have created this new one.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation created/updated or follow-up review issue created
• [-] Code review guidelines
• [-] Merge request performance guidelines
• [-] Style guides
• [-] Database guides
• Separation of EE specific content