remove trailing space

Author: harryhanYuhao

src/doc/rustdoc/src/what-is-rustdoc.md

@@ -34,7 +34,7 @@ the main page is located in `doc/lib/index.html`. If you open that up in
 a web browser, you will see a page with a search bar, and "Crate lib" at the
 top, with no contents.
 
-You can also use `cargo doc` to generate documentation for the whole project. 
+You can also use `cargo doc` to generate documentation for the whole project.
 See [Using rustdoc with Cargo](#rustdoc-cargo).
 
 ## Configuring rustdoc
@@ -79,7 +79,7 @@ Cargo also has integration with `rustdoc` to make it easier to generate
 docs. Instead of the `rustdoc` command, we could have done this:
 
 ```bash
-$ cargo doc 
+$ cargo doc
 $ cargo doc --open # automatically open
 ```