Removes link to full list of topics

* Removing the link will allow us to deploy the services and information
  page without there being an way in the UI to access it.

* Changes features to reflect removing the link

* Actions PR comment for feature scenario clarification
Actions PR comments

* Changes ServicesAndInformationParser:
  make more use of methods available on GdsApi::Response
  assign subsector_link in #parsed_content to :link instead of :slug

* Changes ServicesAndInformationParserTest to check that all necessary
  keys are present in the parsed content instead of relying on checking
  explicit values returned by the rummager test helpers