fix(taskQueue): fix "immediate" rendering (#2630)

With taskQueue: "async" and "congestedAsync" `scheduleUpdate` calls
`writeTask`, passing it the `dispatch` callback. `writeTask` calls the
passed in dispatch callback in `process.nextTick()`

Before this change, when the taskQueue: was set to `immediate`, the
dispatch callback was never called. Resulting in no components rendering
in the DOM.

src/runtime/update-component.ts

@@ -28,7 +28,7 @@ export const scheduleUpdate = (hostRef: d.HostRef, isInitialLoad: boolean) => {
   // has already fired off its lifecycle update then
   // fire off the initial update
   const dispatch = () => dispatchHooks(hostRef, isInitialLoad);
-  return BUILD.taskQueue ? writeTask(dispatch) : dispatch;
+  return BUILD.taskQueue ? writeTask(dispatch) : dispatch();
 };
 
 const dispatchHooks = (hostRef: d.HostRef, isInitialLoad: boolean) => {