Fix style

Author: qinsoon

src/mmtk.rs

@@ -556,6 +556,6 @@ impl<VM: VMBinding> MMTK<VM> {
                 });
             }
         });
-        return ret;
+        ret
     }
 }

src/scheduler/worker.rs

@@ -460,6 +460,6 @@ impl<VM: VMBinding> WorkerGroup<VM> {
             }
             live_bytes_per_space.clear();
         });
-        return ret;
+        ret
     }
 }