message: refactor: specify route instead of href for registries join link
diff: <nav.links.secondary
  data-test-join='1'
  data-analytics-name='Sign up'
  - @href={{this.signUpRoute}}
  + @route='register'
  + @queryParams={{this.signUpQueryParams}}
  @classNames={{local-class 'HideOnMobile'}}
  >
  <h4>{{t 'navbar.join'}}</h4>
  <OsfLink
  data-test-join-mobile
  data-analytics-name='Sign up'
  - @href={{this.signUpRoute}}
  + @route='register'
  + @queryParams={{this.signUpQueryParams}}
  >
  <FaIcon @icon='user-plus' @fixedWidth={{true}} />
  {{t 'navbar.join'}}
  