Fix out-of-date comment (rust-lang#14040)

This comment was left behind when the method receiver was split out from
the method arguments in 4bcadde.

changelog: none

Author: Centri3

clippy_lints/src/methods/unnecessary_sort_by.rs

@@ -44,8 +44,7 @@ fn mirrored_exprs(a_expr: &Expr<'_>, a_ident: &Ident, b_expr: &Expr<'_>, b_ident
                 && iter::zip(*left_args, *right_args).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident))
         },
         // The two exprs are method calls.
-        // Check to see that the function is the same and the arguments are mirrored
-        // This is enough because the receiver of the method is listed in the arguments
+        // Check to see that the function is the same and the arguments and receivers are mirrored
         (
             ExprKind::MethodCall(left_segment, left_receiver, left_args, _),
             ExprKind::MethodCall(right_segment, right_receiver, right_args, _),