fix: use const in the vue shim file, avoiding eslint errors

Author: haoqunjiang

packages/@vue/cli-plugin-typescript/generator/template-vue3/src/shims-vue.d.ts

@@ -1,5 +1,5 @@
 declare module '*.vue' {
   import { Component } from 'vue'
-  var component: Component
+  const component: Component
   export default component
 }