Remove broken link to nested README
Remove broken link to nested README

This was removed in [1].

[1]: https://github.com/alphagov/notifications-utils/commit/332fe76d080738b5a2862c2371b81355e92a427f#diff-0b5ca119d2be595aa307d34512d9679e49186307ef94201e4b3dfa079aa89938

alphagov/notifications-utils