fuchsia-zircon does not depend on core

Change-Id: Ic69d26351d3fb3d94f5ddb8e695bf9218381fe5e
diff --git a/public/rust/crates/fuchsia-zircon/src/lib.rs b/public/rust/crates/fuchsia-zircon/src/lib.rs
index fe6252e..f752075 100644
--- a/public/rust/crates/fuchsia-zircon/src/lib.rs
+++ b/public/rust/crates/fuchsia-zircon/src/lib.rs
@@ -5,7 +5,6 @@
 //! Type-safe bindings for Zircon kernel
 //! [syscalls](https://fuchsia.googlesource.com/zircon/+/master/docs/syscalls.md).
 
-extern crate core;
 extern crate fuchsia_zircon_sys as zircon_sys;
 
 use std::marker::PhantomData;