If you want to get rid of this error, you could either update the Ionic 2 framework to beta.4
or update only Angular 2 to beta.7
as @rapropos suggested.
Here is a good explanation of the difference (you can check out the linked post for more details):
I wrote a short guide on how to upgrade your project to beta.4
if you’re using an older version of the framework (check out the linked post for detailed instructions):