Update roughtime.cloudflare.com public key and port

[lukevalenta]

Fixes #3937. Note that the old Cloudflare public key is still present in test vectors in the codebase in two locations, but this isn't problematic as they don't require the server to be online:

• botan/src/tests/data/roughtime/roughtime_response.vec

  Line 50 in afd43c5

  Pubkey = 803eb78528f749c4bec2e39e1abb9b5e5ab7e4dd5ce4b6f2fd2f93ecc3538f1a

• botan/src/tests/test_roughtime.cpp

  Line 144 in afd43c5

  "ed25519 gD63hSj3ScS+wuOeGrubXlq35N1c5Lby/S+T7MNTjxo= uLeTON9D+2HqJMzK6sYWLNDEdtBl9t/9yw1cVAOm0/sONH5Oqdq9dVPkC9syjuWbglCiCPVF+FbOtcxCkrgMmA== BQAAAEAAAABAAAAApAAAADwBAABTSUcAUEFUSFNSRVBDRVJUSU5EWOw1jl0uSiBEH9HE8/6r7zxoSc01f48vw+UzH8+VJoPelnvVJBj4lnH8uRLh5Aw0i4Du7XM1dp2u0r/I5PzhMQoDAAAABAAAAAwAAABSQURJTUlEUFJPT1RAQg8AUBo+tEqPBQC47l77to7ESFTVhlw1SC74P5ssx6gpuJ6eP+1916GuUiySGE/x3Fp0c3otUGAdsRQou5p9PDTeane/YEeVq4/8AgAAAEAAAABTSUcAREVMRe5T1ml8wHyWAcEtHP/U5Rg/jFXTEXOSglngSa4aI/CECVdy4ZNWeP6vv+2//ZW7lQsrWo7ZkXpvm9BdBONRSQIDAAAAIAAAACgAAABQVUJLTUlOVE1BWFQpXlenV0OfVisvp9jDHXLw8vymZVK9Pgw9k6Edf8ZEhUgSGEc5jwUASHLvZE2PBQAAAAAA\n";

[coveralls]

coverage: 92.017% (-0.002%) from 92.019%
when pulling 5fc72dc on lukevalenta:lvalenta/cloudflare-roughtime
into 8d02e96 on randombit:master.

[randombit]

Thank you