cmd/compile: correct RewriteMultiValueCall fatal message

cmd/compile: correct RewriteMultiValueCall fatal message

The function name was changed in CL 331470.

Change-Id: I6f41866a9c5ccce594dd84185ebfc1c5af280184
Reviewed-on: https://go-review.googlesource.com/c/go/+/596395
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>