cmd/internal/obj/arm64: replace the migrated url address

cmd/internal/obj/arm64: replace the migrated url address

Change-Id: I36a0f0989d37bef45ea8778da799b56a7e9a0c30
Reviewed-on: https://go-review.googlesource.com/c/go/+/529515
Run-TryBot: shuang cui <imcusg@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>