6.4.2.15.
The "Sharing" tab is now a global action
Up one level
The "Sharing" tab now points to the @@sharing view, and is defined as a global action in the object category. If you have a custom content type and you have set up the local_roles action, which would normally be pointing to the folder_localrole_from template, you should remove it. It will be removed from existing, installed types during migration.
If you do not remove the action, the user will see two "Sharing" tabs.
For an example of the canonical set of actions and aliases, see the GenericSetup definition of the Document FTI. Of course, you may not need the References, History or External Edit actions in your own types.