R1:960a1ab1ecd6

Facts: Fix displaying charts for anonymous users

Summary:
Charts in the Facts prototype application (e.g. as a Burndown chart on a project's Reports page) remained empty for users not logged in: payload response was a login dialog instead of actual data to render. Thus set `shouldAllowPublic()` (as for many other Controllers).

Closes T15436

Test Plan:
* As an admin, enable the Facts prototype application.
* As an admin, set "Can Use Application" to "Public" for Projects on http://phorge.