Update Support/get-help link in ? nav menu

What does this MR do and why?

See gitlab-com/www-gitlab-com#14436 (closed) & gitlab-com/www-gitlab-com!118135 (merged). In order to implement the intention of @hsmith-watson, should we use the new get-help link everywhere?

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

Check URL of the ? > Support menu entry

MR acceptance checklist

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