Push Trust Tokens flag expiry to M90.

Change-Id: I968cf53ce3bee336eb478404ab34175fa6755f5c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2416809
Auto-Submit: Steven Valdez <svaldez@chromium.org>
Reviewed-by: David Van Cleve <davidvc@chromium.org>
Commit-Queue: Steven Valdez <svaldez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808363}

chrome/browser/flag-metadata.json

@@ -4412,7 +4412,7 @@
   {
     "name": "trust-tokens",
     "owners": [ "davidvc", "privacy-sandbox-dev" ],
-    "expiry_milestone": 86
+    "expiry_milestone": 90
   },
   {
     "name": "turn-off-streaming-media-caching-always",