refactor: remove useless parameter on action handlers (#1640)

Author: ktsn

src/store.js

@@ -440,15 +440,15 @@ function registerMutation (store, type, handler, local) {
 
 function registerAction (store, type, handler, local) {
   const entry = store._actions[type] || (store._actions[type] = [])
-  entry.push(function wrappedActionHandler (payload, cb) {
+  entry.push(function wrappedActionHandler (payload) {
     let res = handler.call(store, {
       dispatch: local.dispatch,
       commit: local.commit,
       getters: local.getters,
       state: local.state,
       rootGetters: store.getters,
       rootState: store.state
-    }, payload, cb)
+    }, payload)
     if (!isPromise(res)) {
       res = Promise.resolve(res)
     }