This removes date-fns and replaces it with the already used dayjs library. It does not make sense to have two libraries for the same purpose, and dayjs seems to be smaller and its translations are already integrated. Since we have to use dayjs because it is used by the gantt chart, this was the obvious way to go (instead of replacing dayjs with date-fns).
Resolves https://github.com/go-vikunja/vikunja/issues/391
Reviewed-on: https://kolaente.dev/vikunja/vikunja/pulls/3039
Co-authored-by: kolaente <k@knt.li>
Co-committed-by: kolaente <k@knt.li>
021d71b90e