[luci-milo] include experimental for luci.chromium.clang

Bug: 868213
Change-Id: Ic990e6dd681159e7c214bfbba54a460c56bb0588
Reviewed-on: https://chromium-review.googlesource.com/1214563Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Ryan Tseng <hinoka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589735}

infra/config/global/luci-milo.cfg

@@ -2087,6 +2087,7 @@ consoles {
   repo_url: "https://chromium.googlesource.com/chromium/src"
   refs: "refs/heads/master"
   manifest_name: "REVISION"
+  include_experimental_builds: true
 
   builders {
     name: "buildbucket/luci.chromium.ci/ToTLinux"