codegen: Use shorthand initialization in EnumBuilder.

This was introduced in #1850.
diff --git a/src/codegen/mod.rs b/src/codegen/mod.rs
index 20bf54c..7f1232e 100644
--- a/src/codegen/mod.rs
+++ b/src/codegen/mod.rs
@@ -2513,8 +2513,8 @@
                 }
 
                 EnumBuilder::Consts {
-                    repr: repr,
-                    variants: variants,
+                    repr,
+                    variants,
                     codegen_depth: enum_codegen_depth,
                 }
             }