Use helpPagePath to render terraform module registry documentation links

Context

The following discussions from !140215 (merged) should be addressed:

• @justin_ho started a discussion:

  Question (non-blocking): Do we have plans to add anchors / change docs URL any time soon? I see both empty_list_help_url and package_help_url have the same values and was wondering if we have a reason for the 2 attributes. (Btw I personally like to use the helpPagePath frontend helper)

• @justin_ho started a discussion:

  Question (non-blocking): Any particular reason to add the row and col-12 when it's not used yet / we don't have columns? I believe the UI renders the same even without this.

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The empty state URL also points to https://docs.gitlab.com/ee/user/infrastructure/index.html

This should point to https://docs.gitlab.com/ee/user/packages/terraform_module_registry/

Implementation guide

• remove fields empty_list_help_url and package_help_url from https://gitlab.com/gitlab-org/gitlab/-/blob/4ea47547a2b5d087cb2d16e06048cde1ec198363/app/views/groups/infrastructure_registry/index.html.haml
• Remove computed property for emptyListHelpUrl and packageHelpUrl from https://gitlab.com/gitlab-org/gitlab/-/blob/4ea47547a2b5d087cb2d16e06048cde1ec198363/app/assets/javascripts/packages_and_registries/infrastructure_registry/list/components/packages_list_app.vue#L37-41
• Use helpPagePath('user/packages/terraform_module_registry/index') to get the link URLs