[dev.regabi] cmd/compile: clean up ONEW node
[dev.regabi] cmd/compile: clean up ONEW node

The list is no longer needed and can be deleted.
Doing so reduces the inlining cost of any function containing
an explicit call to new by 1 point, so this change is not
toolstash -cmp safe.

Change-Id: Id29e115d68e466a353708ab4b8c1021e9c85a628
Reviewed-on: https://go-review.googlesource.com/c/go/+/274132
Trust: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
Reviewed-by: Matthew Dempsky <e56ac2c500064424afac424d4b5e53bd0570a731@google.com>

CAFxX/go,cloudflare/go,nawawi/go,cloudflare/go,cloudflare/go,golang/go,golang/go,golang/go,cloudflare/go,CAFxX/go,golang/go,CAFxX/go,golang/go,CAFxX/go,nawawi/go,cloudflare/go,cloudflare/go,golang/go,golang/go,CAFxX/go,nawawi/go,CAFxX/go,CAFxX/go,nawawi/go,nawawi/go,nawawi/go,cloudflare/go,CAFxX/go,nawawi/go,nawawi/go,cloudflare/go,golang/go