Change Twitter -> X on bio social media

[petecooper]

Proposal passed muster on moderation thread: https://forum.textpattern.com/viewtopic.php?id=52647

[petecooper]

https://github.com/textpattern/fluxbb/blob/d3c5fc120eac0f35260f582776ed8b3f82a1dee3/profile.php#L869