[CQ] Temporarily exclude broken bot from CQ

TBR=neis@chromium.org

Change-Id: I59903a40c1ca47cce3e5744c51a2abda93e45dad
Reviewed-on: https://chromium-review.googlesource.com/567931Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46580}

infra/config/cq.cfg

@@ -69,7 +69,10 @@ verifiers {
         name: "v8_linux_arm_rel_ng_triggered"
         triggered_by: "v8_linux_arm_rel_ng"
       }
-      builders { name: "v8_linux_chromium_gn_rel" }
+      builders {
+        name: "v8_linux_chromium_gn_rel"
+        experiment_percentage: 100
+      }
       builders { name: "v8_linux_dbg_ng" }
       builders {
         name: "v8_linux_dbg_ng_triggered"