Remove the GetStandardProperties trait.

This was using dynamic dispatch to deal with enums to avoid the repetitive typing.

src/compare/diff.rs

@@ -57,7 +57,6 @@ use crate::types::FixedWidthArea;
 use crate::types::FootnoteDefinition;
 use crate::types::FootnoteReference;
 use crate::types::FootnoteReferenceType;
-use crate::types::GetStandardProperties;
 use crate::types::Heading;
 use crate::types::HorizontalRule;
 use crate::types::Hour;
@@ -413,7 +412,7 @@ pub(crate) fn compare_ast_node<'b, 's>(
             name: rust.get_elisp_fact().get_elisp_name(),
             message: Some(e.to_string()),
             children: Vec::new(),
-            rust_source: rust.get_standard_properties().get_source(),
+            rust_source: rust.get_source(),
             emacs_token: emacs,
         }
         .into()