cmd/compile: remove AllowsGoVersion checks in old typechecker

cmd/compile: remove AllowsGoVersion checks in old typechecker

types2 handles those checks instead.

The only exception is noder.checkEmbed, since when types2
have not known about "//go:embed" pragma yet.

Updates #51691

Change-Id: I74ded03536023fe838f23fa7421e04513f904f66
Reviewed-on: https://go-review.googlesource.com/c/go/+/394556
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>