Increase win10_chromium_x64_rel_ng experiment to 60%

Bug: 756270
Change-Id: I68e4b762f3324c19fe8a20e8d5a180adb6a30305
Reviewed-on: https://chromium-review.googlesource.com/703889Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#506933}

infra/config/cq.cfg

@@ -102,7 +102,7 @@ verifiers {
       builders { name: "win_clang" }
       builders {
         name: "win10_chromium_x64_rel_ng"
-        experiment_percentage: 40
+        experiment_percentage: 60
       }
     }
   }