remove no longer necessary code

Author: yyx990803

src/platforms/web/runtime/components/transition.js

@@ -126,12 +126,6 @@ export default {
     const oldRawChild = this._vnode
     const oldChild: any = getRealChild(oldRawChild)
 
-    // mark v-show
-    // so that the transition module can hand over the control to the directive
-    if (child.data.directives && child.data.directives.some(d => d.name === 'show')) {
-      child.data.show = true
-    }
-
     if (oldChild && oldChild.data && oldChild.key !== key) {
       // replace old child transition data with fresh one
       // important for dynamic transitions!