Extend expiration of Wi-Fi Sync flag to M85.

Bug: 966270
Change-Id: I0261264a0e7b1c4128329902722f33022f842078
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1917756Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Jon Mann <jonmann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715468}

chrome/browser/flag-metadata.json

@@ -3349,7 +3349,7 @@
   {
     "name": "sync-wifi-configurations",
     "owners": ["jonmann", "cros-system-services@google.com"],
-    "expiry_milestone": 80
+    "expiry_milestone": 85
   },
   {
     "name": "system-keyboard-lock",