Feature-gate tracing import.

src/main.rs

@@ -9,6 +9,7 @@ use organic::compare_document;
 use organic::emacs_parse_org_document;
 #[cfg(feature = "compare")]
 use organic::parser::sexp::sexp_with_padding;
+#[cfg(feature = "tracing")]
 use tracing::span;
 
 use crate::init_tracing::init_telemetry;