Remove second primary button from feature flags empty state

Summary

Remove second primary button from feature flags empty state.

There is only one primary button since there can only be one primary button per form. If there is a need for more than one button, the other should be a secondary button.

See https://design.gitlab.com/regions/empty-states#design-specifications.

Steps to reproduce

Go to /feature_flags.

Example Project

See https://gitlab.com/gitlab-org/gitlab-ce/-/feature_flags.

Possible fixes

Since the primary CTA button has moved to the top area navigation, the More information primary button could be changed to a help link as done in many other cases (see helping users).

Current	Proposed