use a more simple fn

Author: tshepang

ci/date-check/src/main.rs

@@ -72,7 +72,7 @@ fn collect_dates_from_file(date_regexes: &[Regex], text: &str) -> Vec<(usize, Da
             .collect();
         output.extend(results);
     }
-    output.sort_by(|a, b| a.0.cmp(&b.0));
+    output.sort_by_key(|a| a.0);
     output
 }