Update milo entry of mac builder perf

Bug: 828468
Change-Id: Ib604bfe647900d3afca46ca6fdcdb5f365d25198
Reviewed-on: https://chromium-review.googlesource.com/1220572Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#590509}

infra/config/global/luci-milo.cfg

@@ -1258,8 +1258,7 @@ consoles {
     short_name: "64"
   }
   builders {
-    name: "buildbot/chromium.perf/Mac Builder Perf"
-    name: "buildbucket/luci.chrome.ci/Mac Builder Perf"
+    name: "buildbucket/luci.chrome.ci/mac-builder-perf"
     category: "builder"
     short_name: "mac"
   }