Extend sharing flags M86->M88

Bug: 1121200
Change-Id: Id33c808f9ec136561be29d44b5b3d726e746347e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2372818Reviewed-by: Travis Skare <skare@chromium.org>
Commit-Queue: Jeffrey Cohen <jeffreycohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801577}

chrome/browser/flag-metadata.json

@@ -4004,7 +4004,7 @@
   {
     "name": "share-button-in-top-toolbar",
     "owners": [ "jeffreycohen" ],
-    "expiry_milestone": 86
+    "expiry_milestone": 88
   },
   {
     "name": "shared-clipboard-ui",