remove no longer relevant code

Author: yyx990803

Diff for: src/core/observer/watcher.js

@@ -216,9 +216,8 @@ export default class Watcher {
     if (this.active) {
       // remove self from vm's watcher list
       // this is a somewhat expensive operation so we skip it
-      // if the vm is being destroyed or is performing a v-for
-      // re-render (the watcher list is then filtered by v-for).
-      if (!this.vm._isBeingDestroyed && !this.vm._vForRemoving) {
+      // if the vm is being destroyed.
+      if (!this.vm._isBeingDestroyed) {
         remove(this.vm._watchers, this)
       }
       let i = this.deps.length