Update cmp.rs

Fixed space

Author: sirh3e

library/core/src/cmp.rs

@@ -541,7 +541,7 @@ impl Ordering {
     /// assert_eq!(result, Ordering::Equal);
     ///
     /// let x: (i64, i64, i64) = (1, 2, 7);
-    /// let y: (i64, i64, i64)  = (1, 5, 3);
+    /// let y: (i64, i64, i64) = (1, 5, 3);
     /// let result = x.0.cmp(&y.0).then_with(|| x.1.cmp(&y.1)).then_with(|| x.2.cmp(&y.2));
     ///
     /// assert_eq!(result, Ordering::Less);