Pleroma.HTTP: TLS v1.3 issues

Hi,

Pleroma seems having hard time when fetching data from instance using TLS v1.3, resulting in this error being displayed:

[info] ['TLS', 32, 'client', 58, 32, 73, 110, 32, 115, 116, 97, 116, 101, 32, 'certify', 32, 'at ssl_handshake.erl:1380 generated CLIENT ALERT: Fatal - Handshake Failure - {bad_cert,invalid_key_usage}', 10]

I actually managed to do a quick&dirty fix on my instance which fix TLS versions to use when doing HTTP requests with hackney: https://gitlab.kokakiwi.net/va-11-hall-a.cafe/pleroma/commit/d9c5cb7fdbdffa60c2d04f4e8b7d9868983bf82a

But maybe there's a cleaner way to fix this, which is why I open this issue.