Remove the outdated 'GOV.UK uses cookies to make the site simpler' cookie banner

[36degrees]

In preparation for the publication of a new cookie banner component in the Design System, remove the old 'GOV.UK uses cookies to make the site simpler' cookie banner from the Prototype Kit.

• Remove the cookie banner from layouts and stylesheets
• Remove the server logic and config for the cookie banner, including a dependency on cookie-parser
• Update the cookies page to remove references to using cookies to record notifications that the user has seen, the seen_cookie_message cookie, and showing a cookie banner or message.

Closes #859

[36degrees]

Verified that if none of the changes are made to the app folder (i.e. if the app folder still includes the partial, stylesheet etc) that this still works as expected – because shouldShowCookieMessage is never set to true, the cookie-banner partial never outputs anything.

(Verified by resetting the app folder to mirror master by running git checkout master app/ and then running the kit)

[EoinShaughnessy]

@36degrees As per style guide advice, can we make the quotes in the issue title single instead of double?

Also, I wonder should we change 'old style' to 'outdated.' 'Old style' seems like plainer English, but in this context we'd be associating 'old' with 'obsolete' - which probably isn't inclusive.

[36degrees]

@EoinShaughnessy good call on both. If it's OK with you, suggest we make those changes at the point we update the release notes to add the version number (as part of the release process)

[EoinShaughnessy]

@36degrees Sounds good!