fixed cargo fmt complaint

src/lib.rs

@@ -163,13 +163,13 @@
 //! \
 //! diagnostic error code: oops::my::bad (link)
 //! Error: oops!
-//! 
+//!
 //! \
 //! Begin snippet for bad_file.rs starting
 //! at line 2, column 3
 //! \
 //! snippet line 1: source
-//! 
+//!
 //! \
 //! snippet line 2:  text
 //!     highlight starting at line 1, column 3: This bit here