Fix Pelican and Sass's verisons and update to latest
The Pelican-Sass image doesn't freeze the Pelican's version. Fix that and set it to the newest. Update the image in https://gitlab.com/ccns/ccns.gitlab.io
The Pelican-Sass image doesn't freeze the Pelican's version. Fix that and set it to the newest. Update the image in https://gitlab.com/ccns/ccns.gitlab.io