cmd/go/internal/modcmd: remove documentation for auto-converting legacy formats
CL 518776 dropped the ability of 'go mod init' to convert
legacy pre-module dependency configuration files, such as automatically
transforming a Gopkg.lock to a go.mod file with similar requirements,
but some of the documentation remained.
In this CL, we remove it from the cmd/go documentation.
(CL 662675 is a companion change that removes it from the Modules
Reference page).
Updates #71537
Change-Id: Ieccc64c811c4c25a657c00e42f7362a32b5fd661
Reviewed-on: https://go-review.googlesource.com/c/go/+/662695 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Michael Matloob <matloob@golang.org> Reviewed-by: Sean Liao <sean@liao.dev>
Auto-Submit: Sean Liao <sean@liao.dev>