Remove linux_chromium_dbg_ng from the CQ experiment

We have the data we need now

Bug: 731434, 813170
Change-Id: I3bd8f4bc5460e214af0041c309cf1ea939290adf
Reviewed-on: https://chromium-review.googlesource.com/923428Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537432}

infra/config/cq.cfg

@@ -100,14 +100,6 @@ verifiers {
         name: "linux_chromium_compile_dbg_ng"
         equivalent_to { bucket: "luci.chromium.try" percentage: 100 }
       }
-      builders {
-        # The only purpose of this builder here is get data for migrating this
-        # builder to LUCI, see https://crbug.com/731434.
-        # TODO(tandrii): remove this builder once enough data has been
-        # collected.
-        name: "linux_chromium_dbg_ng"
-        experiment_percentage: 5
-      }
       builders {
         name: "linux_chromium_headless_rel"
         equivalent_to { bucket: "luci.chromium.try" percentage: 0 }