lang/go125: Update to 1.25.12
Changes:
go1.25.12 (released 2026-07-07) includes security fixes to the crypto/tls and os packages, as well as bug fixes to the compiler, the go command, and the net and os packages.
MFH: 2026Q3
Reviewed by: adamw
Differential Revision: https://reviews.freebsd.org/D58111