Fix typo in Chapter 7 Section 3

Fix typo in Chapter 7 Section 3, changing "start an executable that calls code with the library crate." to "start an executable that calls code within the library crate."

src/ch07-03-paths-for-referring-to-an-item-in-the-module-tree.md

@@ -184,7 +184,7 @@ interested in this topic, see [The Rust API Guidelines][api-guidelines].
 > well as a *src/lib.rs* library crate root, and both crates will have the
 > package name by default. Typically, packages with this pattern of containing
 > both a library and a binary crate will have just enough code in the binary
-> crate to start an executable that calls code with the library crate. This
+> crate to start an executable that calls code within the library crate. This
 > lets other projects benefit from most of the functionality that the package
 > provides, because the library crate’s code can be shared.
 >