I took a look with:
echo | openssl s_client -showcerts -connect www.vim.org:443 2>/dev/null | openssl x509 -text | grep Not Not Before: Jun 10 04:38:43 2023 GMT
Not After : Sep 8 04:38:42 2023 GMT
So it appears that one of their servers has an expired certificate. Most of my results were fine:
echo | openssl s_client -showcerts -connect www.vim.org:443 2>/dev/null | openssl x509 -text | grep Not Not Before: Aug 26 23:34:41 2023 GMT
Not After : Nov 24 23:34:40 2023 GMT
Either a script to update Let's Encrypt certificates is not running properly on that one server, or someone has failed to do a manual update if they do that.