Fix typo in doc

src/libcore/array.rs

@@ -89,7 +89,7 @@ macro_rules! __impl_slice_eq2 {
     }
 }
 
-// macro for implementing n-ary tuple functions and operations
+// macro for implementing n-element array functions and operations
 macro_rules! array_impls {
     ($($N:expr)+) => {
         $(