Rewrite trailing slashes to canonical URL

If user hits https://www.gov.uk/browse/driving/, it redirects to
https://www.gov.uk/browse/driving and does load the correct page.

Currently on mirror, we get a 503 in above scenario, because the
redirection is usually handled by the application.

This commit adds a rewrite which will do that redirection for all URLs
ending in a slash - I've confirmed that we don't have any URLs which
should end in a trailing slash, so this change will make the mirror
match the behaviour of the GOV.UK Stack.

This [Fixes #56337502] once it has been deployed
Remove trailing semicolon

This is added in the template used by the defined type:
https://github.com/alphagov/puppet-nginx-jfryman/blob/master/templates/vhost/vhost_location_directory.erb#L2-L3
Merge pull request #30 from alphagov/rewrite-trailing-slash

Rewrite trailing slashes to canonical URL