Remove LiferayFacesContext Reference

I spoke with Neil about a inconsistency in a Liferay Faces tutorial dealing with the `LiferayFacesContext` and `FacesContext` classes. He recommended we delete the `LiferayFacesContext` reference and use `FacesContext` in the tutorial's code snippet. He characterized the `LiferayFacesContext` class as "semi-deprecated" due to a controversial message in the Liferay Forums, so he'd like to steer away from encouraging the use of that class.

@jhinkey

https://issues.liferay.com/browse/LRDOCS-1520