[dev.typeparams] cmd/compile/internal/types2: remove unused TypeParam.Bound method
[dev.typeparams] cmd/compile/internal/types2: remove unused TypeParam.Bound method

Use TypeParam.Constraint instead.

Change-Id: Iebd77d304f2b7238baa231fb9869c964f66ea355
Reviewed-on: https://go-review.googlesource.com/c/go/+/340990
Trust: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
Reviewed-by: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>

golang/go,cloudflare/go,CAFxX/go,cloudflare/go,CAFxX/go,cloudflare/go,golang/go,nawawi/go,golang/go,nawawi/go,nawawi/go,CAFxX/go,nawawi/go,golang/go,golang/go,nawawi/go,CAFxX/go,cloudflare/go,cloudflare/go,golang/go,cloudflare/go,CAFxX/go,CAFxX/go,CAFxX/go,golang/go,cloudflare/go,nawawi/go,cloudflare/go,nawawi/go,CAFxX/go,golang/go,nawawi/go