Flip brailleDisplayPrivate API to the stable channel.

BUG=293044,178559

Review URL: https://chromiumcodereview.appspot.com/23463038

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@223552 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/extensions/api/_permission_features.json

@@ -95,7 +95,7 @@
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "brailleDisplayPrivate": {
-    "channel": "dev",
+    "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app", "platform_app"],
     "location": "component"
   },