[FIX] reactivity: don't react when we set the same object

The purpose of this commit is to not notify reactivity when an object is
replaced by the same object (same reference) in an reactive object.

src/runtime/reactivity.ts

@@ -249,7 +249,7 @@ function basicProxyHandler<T extends Target>(callback: Callback): ProxyHandler<T
     set(target, key, value, receiver) {
       const hadKey = objectHasOwnProperty.call(target, key);
       const originalValue = Reflect.get(target, key, receiver);
-      const ret = Reflect.set(target, key, value, receiver);
+      const ret = Reflect.set(target, key, toRaw(value), receiver);
       if (!hadKey && objectHasOwnProperty.call(target, key)) {
         notifyReactives(target, KEYCHANGES);
       }