fix(theme): bind missing no icon prop in the menu link component

[dvuckovic]

Building upon #3607 it would be nice to have such control over the dropdown menu links as well.

Use Case

export default {
  themeConfig: {
    nav: [
      {
        text: 'Current release',
        items: [
          text: 'Next release',
          link: 'https://next.example.com',
          target: '_self',
          noIcon: true, // don't want the external link icon here, even though it's on a different domain
        ],
      },
    ],
  },
}