fix: "props" and "emits" has been merged.

[ysy945]

The "props" and "emits" attributes have been merged when creating component instances, so there is no need to merge them here. It's OK to directly reference the previously merged values.
If I declare "emits" and "mixins" at the same time and then access the "emits" attribute through "this. $options" in "setup", the accessed "emits" attribute will not be merged.

<script>
import { h } from "vue";
export default {
  setup() {
    return function () {
      console.log(this.$options);
      return h("div", null, 123);
    };
  },
  emits: ["he"],
  mixins: [
    {
      emits: ["hello"],
    },
  ],
};
</script>

• before updating
  
• after updating the attributes of "emits" is right
  

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[ysy945]

@sxzz

[haoqunjiang]

Already fixed in #8052