Add owners for experimental-productivity-features flag

Added crbug.com/906163 to follow up when the expiry date approaches.

Bug: 906163
Change-Id: Iae7d335eb0be5617066f8f94940061f8b22bc2f6
Reviewed-on: https://chromium-review.googlesource.com/c/1340571Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Ian Clelland <iclelland@chromium.org>
Commit-Queue: Jason Chase <chasej@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610090}

chrome/browser/flag-metadata.json

@@ -1138,7 +1138,7 @@
   },
   {
     "name": "enable-experimental-productivity-features",
-    // "owners": [ "your-team" ],
+    "owners": [ "feature-control@chromium.org" ],
     "expiry_milestone": 76
   },
   {