[dev.unified] cmd/compile: drop package height from Unified IR importer
CL 410342 removed package height, but still needs to keep writing out 0
for iexport for compatibility with existing importers. With Unified IR,
we don't have to, so get rid of the package height completely.
Change-Id: I84a285cbaddd7bb0833d45a24a6818231b4d2b71
Reviewed-on: https://go-review.googlesource.com/c/go/+/411014 Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>