This test already passes for GOEXPERIMENT=unified; add regress test to
ensure it stays that way.
Updates #53477.
Change-Id: Ib7aa7428260595077052207899edcc044a6ab1c8
Reviewed-on: https://go-review.googlesource.com/c/go/+/413394
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: David Chase <drchase@google.com>
