[dev.typeparams] go/types: remove unnecessary guard from NewInterfaceType
This is a partial port of CL 322609, containing only changes to
go/types. Importer changes will be made in a separate CL.
Change-Id: I50af3c1ed5e949bb28a3462d717c0eb29a5f31ab
Reviewed-on: https://go-review.googlesource.com/c/go/+/335144
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>