Copy translations to wp.org and remove files from plugin

These files aren't needed anymore.
We should copy it to translate.wordpress.org and remove the files once the translations are accepted.

**Existing languages**
Available on wp.org and removed in plugin are marked as complete
https://translate.wordpress.org/projects/wp-plugins/widget-css-classes
- [x] nl_NL
- [x] ru_RU
- [ ] es_ES
- [ ] pl_PL
- [ ] sk_SK
- [ ] sr_RS
- [x] sv_SE