[dev.typeparams] cmd/compile/internal/types2: correct error position for...

[dev.typeparams] cmd/compile/internal/types2: correct error position for inherited const init expression

Enabled fixedbugs/issue8183.go for run.go with new typechecker
now that issue is fixed.

Fixes #42992.
Updates #42991.

Change-Id: I23451999983b740d5f37ce3fa75ee756daf1a44f
Reviewed-on: https://go-review.googlesource.com/c/go/+/275517


Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>