Removing PHP recipe execution from php-agent installation.

Any system installing the php plugin agent is already going to have php
installed so this step is redundant and breaks attempts to make the
agent installation stand-alone.

**Explanation**

Please take out including the php recipe.  This is not necessary and does not belong in this recipe.  This belongs in a role/run list.

I want to be able to run this recipe as a standalone without installing other things that the agent depends on.  In almost no circumstance am I going to install the php agent without php already being installed.

The problem is I'm using a php wrapper cookbook to support newer versions of PHP on Amazon but I don't want the steps being taken in that cookbook to run when all I want this the php agent to be installed.