Fix the example syntax for changing the runner tag

What does this MR do?

Fixes an failing spec test in master, by updating our custom tags example to no longer use the deprecated method of setting runner tags.

https://gitlab.com/gitlab-org/charts/gitlab/-/jobs/2664531079 is an example of the failure we are fixing

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

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