Update tests to support Babel 2.15.0

[leamingrad]

As part of the Babel 2.15.0 release, an upgrade to CLDR 44 was included. The new CLDR version changes the date format for the en-GB locale to remove a comma in the full format.

This change updates the tests so that both the old and new formats can be handled. This is done instead of pinning babel to a lower version, since we just care that formatting takes place.