OOR-CORS: Extends expiry milestone

Since we postponed OOR-CORS launch, we will update the
expiry milestone.

Bug: 905971
Change-Id: Ifae7c33745c126e9c08b994db20772de234ff2db
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1781133
Commit-Queue: Takashi Toyoshima <toyoshim@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Auto-Submit: Takashi Toyoshima <toyoshim@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#692410}

chrome/browser/flag-metadata.json

@@ -2716,7 +2716,7 @@
   {
     "name": "out-of-blink-cors",
     "owners": [ "toyoshim" ],
-    "expiry_milestone": 76
+    "expiry_milestone": 80
   },
   {
     "name": "overlay-new-layout",