dashboard: mark all linux-loong64 builders as migrated to LUCI

All builders are now running on LUCI.

Updates golang/go#65398

Change-Id: If2b0703ba0b6defd90d89c42895345eea30fd8cf
Reviewed-on: https://go-review.googlesource.com/c/build/+/585175
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>

dashboard/builders.go

@@ -2918,6 +2918,7 @@ var BuildersPortedToLUCI = map[string]bool{
  "linux-ppc64le-power10osu": true, // Available as https://ci.chromium.org/p/golang/builders/ci/gotip-linux-ppc64le_power10.
  "linux-ppc64-sid-buildlet": true, // Available as https://ci.chromium.org/p/golang/builders/ci/gotip-linux-ppc64_power8.
  "linux-ppc64-sid-power10": true, // Available as https://ci.chromium.org/p/golang/builders/ci/gotip-linux-ppc64_power10.
+ "linux-loong64-3a5000": true, // Available as https://ci.chromium.org/p/golang/builders/ci/gotip-linux-loong64.
 
  "netbsd-arm64-bsiegert": true, // Available as https://ci.chromium.org/p/golang/builders/ci/gotip-netbsd-arm64.