Remove commented out code.

Change-Id: I0b7a41689d04adae1954d21f3bf6e8f8a36b4d0e
diff --git a/src/cswap.rs b/src/cswap.rs
index b509481..44db6db 100644
--- a/src/cswap.rs
+++ b/src/cswap.rs
@@ -1,5 +1,3 @@
-//extern "C" fn swap_loop(a: *mut cty::c_char, b: *mut cty::c_char, n: cty::c_int);
-
 use crate::bindings;
 use std::cmp::min;
 use std::mem::size_of;