[M115] Release ExtensionUnpublishedAvailability policy

Mark the policy as supported on Win, Mac, Linux and Chrome OS, starting
from M115. No ending milestone set currently for now.

(cherry picked from commit 19f41a4)

Bug: 1406308
Change-Id: I436895859151258f1e44c403eccc53d8b0772300
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4562298
Commit-Queue: Anunoy Ghosh <anunoy@chromium.org>
Reviewed-by: Owen Min <zmin@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1148632}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4566259
Cr-Commit-Position: refs/branch-heads/5790@{#27}
Cr-Branched-From: 1d71a33-refs/heads/main@{#1148114}

components/policy/resources/templates/policy_definitions/Extensions/ExtensionUnpublishedAvailability.yaml

@@ -14,9 +14,9 @@ desc: |-
   If the policy is set to <ph name="ALLOW_UNPUBLISHED">AllowUnpublished</ph> (0) or not set, extensions that are unpublished on the Chrome Web Store are allowed.
   If the policy is set to <ph name="DISABLE_UNPUBLISHED">DisableUnpublished</ph> (1), extensions that are unpublished on the Chrome Web Store are disabled.
 
-future_on:
-- chrome.*
-- chrome_os
+supported_on:
+- chrome.*:115-
+- chrome_os:115-
 features:
   dynamic_refresh: true
   per_profile: true