mysql57-{client, server}: Update ports to 5.7.23
This update includes Oracle Critical Patch Advisory published on July 2018
More info:
http://www.oracle.com/technetwork/security-advisory/cpujul2018-4258247.html#AppendixMSQL

PR: 229860
Submitted by: Dani <i.dani@outlook.com<
Reported by: Markus Kohlmeyer <rootservice@gmail.com>
Reviewed by: brnrd , koobs
Sponsored by: The FreeBSD Foundation