Updated flag metadata for the WebRtcUseEchoCanceller3 flag

Bug: webrtc:8671
Change-Id: Ie1d02c21a5c9d1e53b17f929750bd0ed43785dfa
Reviewed-on: https://chromium-review.googlesource.com/c/1355166Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Per Åhgren <peah@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612427}

chrome/browser/flag-metadata.json

@@ -58,7 +58,7 @@
   },
   {
     "name": "WebRtcUseEchoCanceller3",
-    // "owners": [ "your-team" ],
+    "owners": [ "peah@chromium.org", "gustaf@chromium.org" ],
     "expiry_milestone": 76
   },
   {