Fix typo

Author: mdinger

src/doc/tutorial.md

@@ -1736,7 +1736,7 @@ let closure = || -> () { println!("{}", x) }; // can capture enclosing scope
 
 // `fun_arg` is an invalid definition
 fn  fun_arg       (arg: int) -> () { println!("{}", arg + x) }; // cannot capture enclosing scope
-let closure_arg = |arg: int| -> () { println!("{}", arg + x) }; // Can capture enclosing scope
+let closure_arg = |arg: int| -> () { println!("{}", arg + x) }; // can capture enclosing scope
 //                       ^
 // Requires a type because the implementation needs to know which `+` to use.
 // In the future, the implementation may not need the help.