lang/go126: Update to 1.26.6
Changes:
go1.26.6 (released 2026-08-13) includes security fixes to the go command, and the crypto/tls, encoding/asn1, encoding/xml, html/template, net, net/http, and net/url packages, as well as bug fixes to the compiler, the linker, the runtime, and the crypto/tls and os packages.
MFH: 2026Q3