chore: remove preload plugin from deps for now

We are not going to add it back anytime soon. So removing it help
reduces the bundle size.

Though webpack 5 and html-webpack-plugin 5 support was added to
the plugin, there are still tests to be done for compatibility with
the new default configurations.
For example, we need to see how the new `defer` option affects the
result.

Author: haoqunjiang

packages/@vue/cli-service/lib/config/app.js

@@ -112,7 +112,7 @@ module.exports = (api, options) => {
         .plugin('html')
           .use(HTMLPlugin, [htmlOptions])
 
-      // FIXME: preload plugin is not compatible with webpack 5 / html-webpack-plugin 4 yet
+      // FIXME: need to test out preload plugin's compatibility with html-webpack-plugin 4/5
       // if (!isLegacyBundle) {
       //   // inject preload/prefetch to HTML
       //   webpackConfig

packages/@vue/cli-service/package.json

@@ -32,7 +32,6 @@
     "@vue/cli-plugin-vuex": "^5.0.0-alpha.7",
     "@vue/cli-shared-utils": "^5.0.0-alpha.7",
     "@vue/component-compiler-utils": "^3.1.2",
-    "@vue/preload-webpack-plugin": "^1.1.0",
     "@vue/web-component-wrapper": "^1.3.0",
     "acorn": "^8.0.5",
     "acorn-walk": "^8.0.2",