feat(author-archive): replace twitter icon with x

[adekbadek]

All Submissions:

• [x] Have you followed the Newspack Contributing guideline?
• [x] Does your code follow the WordPress' coding standards and VIP Go coding standards?
• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Updates the Twitter bird to X's X for author archives.

How to test the changes in this Pull Request:

1. Edit an author, with wordpress-seo active and at the latest version, and makes sure "X username (without @)" is filled
2. Visit the author archive, observe the X logo instead of the Twitter bird logo

Other information:

• [x] Have you added an explanation of what your changes do and why you'd like us to include them?
• [ ] Have you written new tests for your changes, as applicable?
• [x] Have you successfully ran tests with your changes locally?

---

• To see the specific tasks where the Asana app for GitHub is being used, see below:
  • https://app.asana.com/0/0/1206366882361981

[github-actions[bot]]

Hey @adekbadek, good job getting this PR merged! :tada:

Now, the needs-changelog label has been added to it.

Please check if this PR needs to be included in the "Upcoming Changes" and "Release Notes" doc. If it doesn't, simply remove the label.

If it does, please add an entry to our shared document, with screenshots and testing instructions if applicable, then remove the label.

Thank you! :heart:

[matticbot]

:tada: This PR is included in version 2.3.0-alpha.1 :tada:

The release is available on GitHub release

Your semantic-release bot :package::rocket: