net/croc: Relax the Go version pin to a minimum

croc's go.mod requires go 1.27.0, above the current GO_DEFAULT of 1.26, so
this is one of the rare ports that genuinely needs a version requirement.
Use the floating go:1.27+ form instead of an exact pin so the port moves to
the default once 1.27 becomes it, rather than being removed along with
lang/go127.

Dropping the requirement entirely still built, but only because the fetch
phase downloaded golang.org/toolchain@v0.0.1-go1.27.0.freebsd-amd64 and
built with that instead of the declared go126 dependency.