Send 66% of CQ tryjobs to LUCI's mac_chromium_compile_dbg_ng.

R=jchinlee

Bug: 731545
Change-Id: Ieeb3df10e3649063679cf66a8b9231813714b34b
No-Try: True
Reviewed-on: https://chromium-review.googlesource.com/947566
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Jao-ke Chin-Lee <jchinlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540705}

infra/config/branch/cq.cfg

@@ -141,7 +141,7 @@ verifiers {
       }
       builders {
         name: "mac_chromium_compile_dbg_ng"
-        equivalent_to { bucket: "luci.chromium.try" percentage: 25 }
+        equivalent_to { bucket: "luci.chromium.try" percentage: 66 }
       }
       builders {
         name: "mac_chromium_rel_ng"