Move expiry of zero-state-reinstall flag to M90.

Bug: 911427
Change-Id: Ib3ffd449c8772ac7993b861255c5ecc6ebcb55e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2087499
Auto-Submit: Rob Schonberger <robsc@chromium.org>
Commit-Queue: Jenny Zhang <jennyz@chromium.org>
Reviewed-by: Jenny Zhang <jennyz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747334}

chrome/browser/flag-metadata.json

@@ -2105,7 +2105,7 @@
   {
     "name": "enable-zero-state-app-reinstall-suggestions",
     "owners": ["robsc", "napper", "jennyz"],
-    "expiry_milestone": 80
+    "expiry_milestone": 90
   },
   {
     "name": "enable-zero-state-suggestions",