Fix trailing whitespace.

library/std/src/os/unix/io/mod.rs

@@ -46,7 +46,7 @@
 //!
 //! ## `/proc/self/mem` and similar OS features
 //!
-//! Some platforms have special files, such as `/proc/self/mem`, which 
+//! Some platforms have special files, such as `/proc/self/mem`, which
 //! provide read and write access to the process's memory. Such reads
 //! and writes happen outside the control of the Rust compiler, so they do not
 //! uphold Rust's memory safety guarantees.