[cq] Make chromium win trybot blocking

BUG=chromium:474921
NOTRY=true

Review-Url: https://codereview.chromium.org/2148673004
Cr-Commit-Position: refs/heads/master@{#37765}

infra/config/cq.cfg

@@ -109,10 +109,7 @@ verifiers {
     }
     buckets {
       name: "master.tryserver.chromium.win"
-      builders {
-        name: "win_chromium_compile_dbg_ng"
-        experiment_percentage: 100
-      }
+      builders { name: "win_chromium_compile_dbg_ng" }
     }
   }