docs: Correct examples for cargo_bin!

Fixes #249

Author: epage

src/macros.rs

@@ -48,8 +48,7 @@ macro_rules! crate_name {
 ///
 /// use std::process::Command;
 ///
-/// let mut cmd = Command::new(cargo_bin!())
-///     .unwrap();
+/// let cmd = Command::new(cargo_bin!())
 /// let output = cmd.unwrap();
 /// ```
 #[macro_export]
@@ -78,8 +77,7 @@ macro_rules! cargo_bin {
 ///
 /// use std::process::Command;
 ///
-/// let mut cmd = cargo_bin_cmd!()
-///     .unwrap();
+/// let cmd = cargo_bin_cmd!()
 /// let output = cmd.unwrap();
 /// ```
 #[macro_export]