all: remove support for windows/arm

all: remove support for windows/arm

Also CL 690655 for golang.org/x/sys.

For #71671

Change-Id: Iceb369dec5affb944a39d07cdabfd7add6f1f319
Reviewed-on: https://go-review.googlesource.com/c/go/+/648795
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>