Extend expiry of double-tap-to-zoom-in-tablet-mode flag

TBR=oshima@chromium.org
BUG=none

Change-Id: I2b483d216edc3d12c8b64a926d0e68de6efdfab0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2064814
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742800}

chrome/browser/flag-metadata.json

@@ -868,8 +868,8 @@
   },
   {
     "name": "double-tap-to-zoom-in-tablet-mode",
-    "owners": [ "afakhry" ],
-    "expiry_milestone": 80
+    "owners": [ "afakhry", "tbuckley" ],
+    "expiry_milestone": 85
   },
   {
     "name": "download-auto-resumption-native",