Update cq.cfg to use luci.infra.try bucket instead of luci.infra.depot_tools.try.

Buildbucket config changed here:
  https://chromium-review.googlesource.com/c/infra/infra/+/755313 

TBR=phajdan.jr@chromium.org

Bug: 780352
Change-Id: Ie80d578be7d91108c60bbfb59f8184bc237e4408
Reviewed-on: https://chromium-review.googlesource.com/755315
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>

infra/config/cq.cfg

@@ -16,13 +16,14 @@ verifiers {
 
   try_job {
     buckets {
-      name: "luci.infra.depot_tools.try"
+      name: "luci.infra.try"
       builders { name: "Depot Tools Presubmit" }
-      builders { name: "build Roll Tester" }
-      builders { name: "infra Roll Tester" }
-      builders { name: "skia Roll Tester" }
-      builders { name: "skiabuildbot Roll Tester" }
+      builders { name: "Build downstream Recipe Roll tester from Depot Tools" }
+      builders { name: "Infra downstream Recipe Roll tester from Depot Tools" }
+      builders { name: "Skia downstream Recipe Roll tester from Depot Tools" }
+      builders { name: "Skia Buildbot downstream Recipe Roll tester from Depot Tools" }
     }
+
     buckets {
       name: "master.internal.infra.try"
       builders { name: "build_limited Roll Tester (depot_tools)" }