Replace Twitter bird with X logo on /sharing page

[ezwelty]

The link to our X page was updated (https://github.com/falling-fruit/falling-fruit-web/issues/495), but I just realized that the same needs to be done on the sharing page, where we still display the old Twitter logo when linking to other organizations: https://beta.fallingfruit.org/sharing

@ahmedhalac Interested 😉 ?

[ahmedhalac]

@ezwelty sure. Will take this one.