Allow clippy::ref_option lint for serde::format_description.

Author: wojciech-graj

time-macros/src/serde_format_description.rs

@@ -103,6 +103,7 @@ pub(crate) fn build(
 
     let serialize_option = if cfg!(feature = "formatting") {
         quote! {
+            #[allow(clippy::ref_option)]
             pub fn serialize<S: ::serde::Serializer>(
                 option: &Option<__TimeSerdeType>,
                 serializer: S,