[WEB-3889] chore: remove old fanout, push, realtime compare pages

[jamiehenson]

NOTE TO REVIEWERS - please do not review PRs in the DRAFT state, as the PR may change substantially before it is ready to review. Thanks.

Description

https://ably.atlassian.net/browse/WEB-3889

In prod, these pages will redirect to /compare/all.

[kennethkalmer]

@jamiehenson done, was simple enough to search for compare/ in the content directory to see nothing is referencing these partials, and ditto for the images after removing the partials.

[jamiehenson]

Alrighty then