Migrate twitter.svg references to x.svg

Problem

We've updated twitter.svg to the new X logo. In User profile settings: Rename Twitter to X (#428454 - closed) we're updating the text references, as well. However, as part of the process for deprecating the old Twitter logo, we'll have to go through and replace all old twitter.svg references in the product with the updated x.svg reference. Once this migration has occurred, we can remove the old twitter.svg logo from the svg library.