Mark the module as obsolete and provide an upgrade path

Never mind, the module isn't actually obsolete: it provides 'update/delete own' permissions that core doesn't provide. This means that we should create a new version that converts part of the permissions to the ones provided by core, while keeping the others in this module.

What we could do is log a message in the update hook in case no roles are using permissions provided by this module anymore, which means that the module can be removed.