Fix backup spec navigation

What does this MR do?

Fix backup spec navigation

Fix navigation to test issue, which now
must be in format of:
  <group+project>/-/issues/<issue_id>
instead of:
  <group+project>/issues/<issue_id>

Changelog: fixed

---

Fixes a spec failure in review_specs jobs, for example, experienced in https://gitlab.com/gitlab-org/charts/gitlab/-/jobs/4293464350 and https://gitlab.com/gitlab-org/charts/gitlab/-/jobs/4293464851. Investigating the capybara screenshots shows 404 errors.

Failures:
  1) Restoring a backup Restored gitlab instance Issue attachments should load correctly
     Failure/Error: expect(page).to have_selector(image_selector)
       expected to find css "div.md > p > a > img.js-lazy-loaded" but there were no matches
     # ./spec/features/backups_spec.rb:75:in `block (3 levels) in <top (required)>'
     # ./gems/ruby/3.0.0/gems/rspec-retry-0.6.1/lib/rspec/retry.rb:123:in `block in run'
     # ./gems/ruby/3.0.0/gems/rspec-retry-0.6.1/lib/rspec/retry.rb:110:in `loop'
     # ./gems/ruby/3.0.0/gems/rspec-retry-0.6.1/lib/rspec/retry.rb:110:in `run'
     # ./gems/ruby/3.0.0/gems/rspec-retry-0.6.1/lib/rspec_ext/rspec_ext.rb:12:in `run_with_retry'
     # ./gems/ruby/3.0.0/gems/rspec-retry-0.6.1/lib/rspec/retry.rb:37:in `block (2 levels) in setup'

Related issues

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
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Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.