Drop extra text from Listing[caption]

Author: chriskrycho

src/ch01-03-hello-cargo.md

@@ -58,7 +58,7 @@ repository; you can override this behavior by using `cargo new --vcs=git`.
 Open *Cargo.toml* in your text editor of choice. It should look similar to the
 code in Listing 1-2.
 
-<Listing number="1-2" file-name="Cargo.toml" caption="Listing 1-2: Contents of *Cargo.toml* generated by `cargo new`">
+<Listing number="1-2" file-name="Cargo.toml" caption="Contents of *Cargo.toml* generated by `cargo new`">
 
 ```toml
 [package]