test/codegen: remove plan9/amd64 specific array zeroing/copying tests
The compiler previously avoided the use of MOVUPS on plan9/amd64. This
was changed in CL 655875, however the codegen tests were not updated
and now fail (seemingly the full codegen tests do not run anywhere,
not even on the longtest builders).
Change-Id: I388b60e7b0911048d4949c5029347f9801c018a9
Reviewed-on: https://go-review.googlesource.com/c/go/+/656997
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Auto-Submit: Keith Randall <khr@google.com>