main/links: upgrade to 2.25, fix project url

Upgrade to 2.25 and fix project url

=== RELEASE 2.25 ===

Fri Oct 1 18:27:25 CEST 2021 mikulas:

Delete the expired Let's encrypt certificate from the builtin
certificate store

Thu Sep 30 21:45:10 CET 2021 mikulas:

Set the flag X509_V_FLAG_TRUSTED_FIRST, so that Let's encrypt works
with openssl-1.0.2