Fix filter_map_identity clippy lint

ofborg/src/commentparser.rs

@@ -48,7 +48,7 @@ named!(
                 value!(None, many_till!(take!(1), tag_no_case!("@grahamcofborg")))
                 )
             )))) >> eof!()
-                >> (Some(res.into_iter().filter_map(|x| x).collect()))
+                >> (Some(res.into_iter().flatten().collect()))
         ) | value!(None)
     )
 );