Fix benchmark build

src/ledger.rs

@@ -70,13 +70,4 @@ mod bench {
             assert!(verify_slice(&events, &start_hash));
         });
     }
-
-    #[bench]
-    fn event_bench_seq(bencher: &mut Bencher) {
-        let start_hash = Default::default();
-        let events = next_ticks(&start_hash, 10_000, 8);
-        bencher.iter(|| {
-            assert!(verify_slice_seq(&events, &start_hash));
-        });
-    }
 }