Force SSL for main website instead of optional SSL

https://nixos.wiki/wiki/Nginx
Signed-off-by: Egor Savkin <es@m-labs.hk>

nixbld-etc-nixos/configuration.nix

@@ -781,7 +781,7 @@ in
     recommendedTlsSettings = true;
     virtualHosts = let
       mainWebsite = {
-        addSSL = true;
+        forceSSL = true;
         enableACME = true;
         root = "${hydraWwwOutputs}/web";
         extraConfig = ''