Website: update about page

• Strip core people until if/when we define what that is? The more productive thing right now is probably to just add a maintainers file or similar in our repositories.
• We started operating our own mailing list a while back, i.e., not sponsored by DFRI anymore. (Should we list past sponsors and what they did?)
• Glasklar Teknik AB is the only funder; a new sibling company to Mullvad VPN.