nixos/nginx: re-enable ssl_session_tickets

Mozilla's [recommendations][1] no longer include this item. Per
[mozilla/server-side-tls#135][2] and
[mozilla/ssl-config-generator#252][3], it sounds like versions of nginx
prior to 1.23.2 (released 2022-10-19) didn't make it easy to properly
rotate the ticket encryption keys, but since that version it's now done
automatically. Since nixos-24.05 is already on nginx-1.26.2, it seems
safe to remove this option.

[1]: https://ssl-config.mozilla.org/#server=nginx&config=intermediate
[2]: mozilla/server-side-tls#135
[3]: mozilla/ssl-config-generator#252

nixos/modules/services/web-servers/nginx/default.nix

@@ -186,8 +186,6 @@ let
 
         ssl_session_timeout 1d;
         ssl_session_cache shared:SSL:10m;
-        # Breaks forward secrecy: https://github.com/mozilla/server-side-tls/issues/135
-        ssl_session_tickets off;
         # We don't enable insecure ciphers by default, so this allows
         # clients to pick the most performant, per https://github.com/mozilla/server-side-tls/issues/260
         ssl_prefer_server_ciphers off;