registerServiceWorker import not being removed from main.js when using semicolons

Hello, another quick fix here.

When invoking this plugin in a project with the pwa plugin and an eslint config that uses semicolons, the `registerServiceWorker` import line is not removed from `main.js`.

This can be resolved by doing this
```diff
-contents = contents.replace(/import ('|")\.\/registerServiceWorker('|")\n/, ``)
+contents = contents.replace(/import ('|")\.\/registerServiceWorker('|");?\n/, ``)
```

Here https://github.com/Akryum/vue-cli-plugin-ssr/blob/master/generator/index.js#L47