Update certificates used by PageDomain Factories

Problem

The certificates used in https://gitlab.com/gitlab-org/gitlab/-/blob/master/spec/factories/pages_domains.rb are set to expire on 2020-04-12 which is causing tests to fail due to the PagesDomain.need_auto_ssl_renewal is filtering elements less than SSL_RENEWAL_THRESHOLD.from_now.

See #210557 (comment 304728950) for more detail

Potential Solution

Update the test-certifcates used by the factory and remove the timecop fix implemented with !27239 (merged)