main.star: delete windows/arm (32-bit ARM) builders

There is no running builder for windows/arm. The port was marked broken
in Go 1.24, and it's removed in Go 1.26. At this point no one will be
adding this builder, so remove its definition.

For golang/go#67308.
For golang/go#71671.

Change-Id: I4de21dba07e4fddaf8bd84788c6a132af9098c81
Reviewed-on: https://go-review.googlesource.com/c/build/+/730920
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
4 files changed