Additional spacing below "side navigation" on smaller screen sizes

[leenagupte]

Initially spotted here: #4600 (review)

On < tablet screen sizes additional spacing has been introduced above the “Related Content” section. This is because in this app, the shared sidebar navigation component (which contains “Related Content”) is wrapped in a div with a sidebar-navigation class which adds margin-top: govuk-spacing(7); on smaller screens.

The screenshots show the same content rendered by government-frontend and frontend

government-frontend	frontend