Replace Zendesk FAB with help page link for HCA DCP

[MillenniumFalconMechanic]

Replace the floating action button (FAB) Zendesk support form with a link to the HCA Data Portal help page for the HCA DCP site config.

This mirrors the change already made for AnVIL CMG in #4873 and aligns with the data-portal changes in DataBiosphere/data-portal#3104.