State Module, not State Declaration

In practice, and in many places in the docs, we use the phrase `state declaration` to mean a few different things. Sometimes we call the `file.managed` piece a state declaration. Sometimes we call the entire state stanza a state declaration. But in my experience, nobody calls the `file` piece of `file.managed` the state declaration -- rather, we call that the state module.

@thatch45 should OK this fix, but I think it fits much better.