go/types: remove 1.18 APIs that have been replaced
Remove the Interface.IsConstraint, Signature.SetTypeParams, and
Signature.SetRecvTypeParams methods, as they have been replaced and
usage removed from x/tools.
Change-Id: I8786c3cf34e96ab5211cd8e7e6348e9ee792b843
Reviewed-on: https://go-review.googlesource.com/c/go/+/353570
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>