luci-config: remove known issue for netbsd-arm

Part of golang/go#63698.

Change-Id: Ib1c5722aba24095d27c23cb69065a80d4c127dd4
Reviewed-on: https://go-review.googlesource.com/c/build/+/624995
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: bsiegert