Fix formatting

Author: abhijeetbhagat

src/libstd/process.rs

@@ -260,7 +260,7 @@ impl fmt::Debug for ChildStderr {
 /// ```
 /// use std::process::Command;
 ///
-/// let output = if cfg!(target_os = "windows"){
+/// let output = if cfg!(target_os = "windows") {
 ///     Command::new("cmd")
 ///             .args(&["/C", "echo hello"])
 ///             .output()