FIX: Clean up emoji name which is file name (PR #14980)

Uppy adds the file name as the “name” parameter in the payload by default, which means that for things like the emoji uploader which have a name param used by the controller, that param will be passed as the file name. We already use the existing file name if the name param is null, so this commit just does further cleanup of the name param, removing the extension if it is a filename so we don’t end up with emoji names like blah_png.