webauthn: extend caBLE v2 flag until M87.

Change-Id: Ic7da643ae9bb4e946059e120b333752e043a3976
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2155806
Auto-Submit: Adam Langley <agl@chromium.org>
Commit-Queue: Martin Kreichgauer <martinkr@google.com>
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Cr-Commit-Position: refs/heads/master@{#760585}

chrome/browser/flag-metadata.json

@@ -2190,7 +2190,7 @@
   {
     "name": "enable-web-authentication-cable-v2-support",
     "owners": [ "webauthn-team@google.com" ],
-    "expiry_milestone": 84
+    "expiry_milestone": 87
   },
   {
     "name": "enable-web-bluetooth-new-permissions-backend",