The standard library added errors.ErrUnsupported in Go 1.21. Re-export
it from this package for drop-in compatibility.

Co-Authored-By: roachdev-claude <roachdev-claude-bot@cockroachlabs.com>

Bumps google.golang.org/grpc from 1.56.3 to 1.79.3, addressing the
critical security advisory. Rebased onto current master (go 1.25.0):
the go directive and CI matrix from the original dependabot PR were
stale, so this re-applies only the dependency upgrade on top of master.

go mod tidy pulls the required transitive bumps (protobuf 1.36.10,
golang/protobuf 1.5.4, x/net 0.48.0, x/sys 0.39.0, x/text 0.32.0).

Co-Authored-By: roachdev-claude <roachdev-claude-bot@cockroachlabs.com>

….golang.org/grpc-1.79.3

Bump google.golang.org/grpc from 1.56.3 to 1.79.3

errors: re-export ErrUnsupported from stdlib