Refactor test method version_link_regexp

Related MR: !118678 (merged)

What does this MR do and why?

	GitLab Inc	JiHu GitLab
Host	gitlab.com	jihulab.com
Group path	gitlab-org	gitlab-cn
Project path	gitlab	gitlab
URL	https://gitlab.com/gitlab-org/gitlab	https://jihulab.com/gitlab-cn/gitlab

Using hardcodes in tests will cause JH's pipelines to fail.

Failed job in JiHu: https://jihulab.com/gitlab-cn/gitlab/-/jobs/7518144

cc JH EM @mtan-gitlab

Screenshots or screen recordings

Non-UI

How to set up and validate locally

bundle exec rspec spec/views/help/index.html.haml_spec.rb

MR acceptance checklist

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