Format struct update syntax like rustfmt
diff --git a/src/derive.rs b/src/derive.rs
index e1cb110..0fffff1 100644
--- a/src/derive.rs
+++ b/src/derive.rs
@@ -99,7 +99,7 @@
                     attrs: attrs,
                     generics: Generics {
                         where_clause: wh,
-                        .. generics
+                        ..generics
                     },
                     data: Data::Struct(DataStruct {
                         struct_token: s,
@@ -114,7 +114,7 @@
                     attrs: attrs,
                     generics: Generics {
                         where_clause: wh,
-                        .. generics
+                        ..generics
                     },
                     data: Data::Enum(DataEnum {
                         variants: variants,