WSTEAMA-1565 - Remove old route pattern matcher

[louisearchibald]

Resolves JIRA [1565]

Overall changes

Clean-up PR to remove a route matcher and that follows a URL pattern we are no longer using.

Code changes

• Removes the old pattern route matcher.
• Removes any references to the deleted route matcher.
• Removes old batch of topic tests which previously tested the old route.
• Renames the new route matcher from getVariantTopicPageRegex to be getTopicPageRegex. (same name as the old name, but with URL pattern updated).
• Updates all references to new route matcher with the updated name.
• Removes old snapshots.