style(prost-build): Use enum getter

Use enum getter function to compare enum values instead of `i32` values.

prost-build/src/code_generator.rs

@@ -402,7 +402,7 @@ impl CodeGenerator<'_> {
 
     fn append_field(&mut self, fq_message_name: &str, field: &Field) {
         let type_ = field.descriptor.r#type();
-        let repeated = field.descriptor.label == Some(Label::Repeated as i32);
+        let repeated = field.descriptor.label() == Label::Repeated;
         let deprecated = self.deprecated(&field.descriptor);
         let optional = self.optional(&field.descriptor);
         let boxed = self.boxed(&field.descriptor, fq_message_name, None);
@@ -1069,7 +1069,7 @@ impl CodeGenerator<'_> {
         fq_message_name: &str,
         oneof: Option<&str>,
     ) -> bool {
-        let repeated = field.label == Some(Label::Repeated as i32);
+        let repeated = field.label() == Label::Repeated;
         let fd_type = field.r#type();
         if !repeated
             && (fd_type == Type::Message || fd_type == Type::Group)