[Sharesheet] Update flag expiry milestone.

Bug: 1157709
Change-Id: I67e0fa6488a7bd8c0fa980372dba3a8444dd2c6b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586170
Auto-Submit: Melissa Zhang <melzhang@chromium.org>
Commit-Queue: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836519}

chrome/browser/flag-metadata.json

@@ -2177,7 +2177,7 @@
   {
     "name": "enable-sharesheet",
     "owners": [ "chromeos-apps-foundation-team@google.com" ],
-    "expiry_milestone": 89
+    "expiry_milestone": 92
   },
   {
     "name": "enable-sharesheet-content-previews",