contrib/tzdata: import tzdata 2025b
Changes: https://github.com/eggert/tz/blob/2025b/NEWS
Approved by: so
Security: FreeBSD-EN-25:04.tzdata
(cherry picked from commit d2cccdef30376b7de5643caae1ef035f8e6932f0)
(cherry picked from commit 7b17666c32f7cad4a26cc9da2d3347dca90af32e)