Update libloading to 0.7.3

Test: cd external/rust/crates && atest --host -c
Change-Id: I1a047668c589c6e149a693e9a8ac9e7e9ecbb325
diff --git a/tests/constants.rs b/tests/constants.rs
index ad910c4..6ae5a84 100644
--- a/tests/constants.rs
+++ b/tests/constants.rs
@@ -1,5 +1,5 @@
-extern crate libloading;
 extern crate libc;
+extern crate libloading;
 extern crate static_assertions;
 
 #[cfg(all(test, unix))]