Remove fat_ptr_transmutes lint. It has been removed in Rust 1.23

oherrala · briansmith · commit 44384f81a331 · 2018-04-13T09:46:48.000-10:00
diff --git a/src/untrusted.rs b/src/untrusted.rs
@@ -98,7 +98,6 @@
 #![forbid(
     anonymous_parameters,
     box_pointers,
-    fat_ptr_transmutes,
     legacy_directory_ownership,
     missing_docs,
     trivial_casts,
