Do not pass 'unit' into determine_unit_from_results

src/export/markdown.rs

@@ -28,7 +28,7 @@ pub struct MarkdownExporter {}
 
 impl Exporter for MarkdownExporter {
     fn serialize(&self, results: &[BenchmarkResult], unit: Option<Unit>) -> Result<Vec<u8>> {
-        let unit = determine_unit_from_results(results, unit);
+        let unit = unit.unwrap_or_else(|| determine_unit_from_results(&results));
         let entries = relative_speed::compute(results);
         if entries.is_none() {
             return Err(anyhow!(