dPWA: Bump file-handling-api flag milestone to M88

Bumping file-handling-api flag from expiry milestone M82 to M88
so it continues to exist in the Chrome UI.  While here, I'm
removing oyiptong from owners, adding myself, and removing
the @chromium.org portions to align with other flag entries.

Bug: 1096282
Change-Id: Iae5905a8a112cd8921f22842d11aeaa75e1eaf58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2250931
Auto-Submit: Chase Phillips <cmp@chromium.org>
Commit-Queue: Chase Phillips <cmp@chromium.org>
Commit-Queue: Olivier Yiptong <oyiptong@chromium.org>
Reviewed-by: Olivier Yiptong <oyiptong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#780520}

chrome/browser/flag-metadata.json

@@ -2553,8 +2553,8 @@
   },
   {
     "name": "file-handling-api",
-    "owners": ["mgiuca@chromium.org", "oyiptong@chromium.org"],
-    "expiry_milestone": 82
+    "owners": ["mgiuca", "cmp"],
+    "expiry_milestone": 88
   },
   {
     "name": "files-ng",