Re-add adfree.usableprivacy.net (certificate issue)

[markushuber]

Commit 0899a2a4902267caac6699e3340d9b22d1c83d0d removed our public resolver.

Interesting enough, our monitoring did not detect any service disruptions. Your build pipelines indicated a certificate hash issue (initially with with this PR). This PR updates our servers stamps based on the Let's Encrypt R10 hash from https://github.com/DNSCrypt/doh-server?tab=readme-ov-file#common-certificate-hashes

Overall: It would imho make more sense if one could pin a certain Root CA (e.g. Let's Encrypt) in the dnsstamp instead of intermediate CAs.

P.S.: Any chance that a contact can be provided to enable notification for cases whenever a specific resolver is removed?