[Extensions] Expose host_permissions manifest key in stable

Was previously (erroneously) restricted to dev. This hotfix fixes that

Bug: 1162860
Change-Id: I27e588f9027a36fe9c8e0e8cad8c242dc117f833
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2612205Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Kelvin Jiang <kelvinjiang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840431}

extensions/common/api/_manifest_features.json

@@ -161,7 +161,7 @@
     }
   ],
   "host_permissions": {
-    "channel": "dev",
+    "channel": "stable",
     "extension_types": ["extension"],
     "min_manifest_version": 3
   },