WebApps: Updates expiry on FileHandlingAPI flag.

Bug: 829689
Change-Id: I525854254fd2e9fc2bad57c87ffdaa9175e452a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1865740Reviewed-by: Alan Cutter <alancutter@chromium.org>
Commit-Queue: Jay Harris <harrisjay@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707203}

chrome/browser/flag-metadata.json

@@ -2101,7 +2101,7 @@
   {
     "name": "file-handling-api",
     "owners": ["harrisjay@chromium.org", "raymes@chromium.org"],
-    "expiry_milestone": 79
+    "expiry_milestone": 82
   },
   {
     "name": "file-manager-feedback-panel",