Replace win_chromium_rel_ng with win7_chromium_rel_ng on CQ

Bug: 769870
Change-Id: Icbd3f71ee151fd4a6f17df2de0fbf5bef3f42d9b
Reviewed-on: https://chromium-review.googlesource.com/691518
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: smut <smut@google.com>
Cr-Commit-Position: refs/heads/master@{#505273}

infra/config/cq.cfg

@@ -95,17 +95,11 @@ verifiers {
     }
     buckets {
       name: "master.tryserver.chromium.win"
+      builders { name: "win7_chromium_rel_ng" }
       builders { name: "win_chromium_compile_dbg_ng" }
-      builders {
-        name: "win_chromium_rel_ng"
-      }
       # crbug.com/753184 - take out of the CQ temporarily.
       # builders { name: "win_chromium_x64_rel_ng" }
       builders { name: "win_clang" }
-      builders {
-        name: "win7_chromium_rel_ng"
-        experiment_percentage: 100
-      }
       builders {
         name: "win10_chromium_x64_rel_ng"
         experiment_percentage: 20