lang/go124: Update to 1.24.6
While here:
- golang.org now points to go.dev (see Review below, thanks to Meng Zhuo)
- Update the bootstrap version to bring in various compiler improvements.
Changes:
go1.24.6 (released 2025-08-06) includes security fixes to the database/sql and os/exec packages, as well as bug fixes to the runtime. See the Go 1.24.6 milestone (follows) on our issue tracker for details. https://github.com/golang/go/issues?q=milestone%3AGo1.24.6+label%3ACherryPickApproved
Differential Revision: https://reviews.freebsd.org/D50595