Fixes the scheme

just to be sure.

nginx.conf

@@ -30,10 +30,10 @@ http {
     }
 
     location = /.well-known/carddav {
-      return 301 $scheme://$host/remote.php/dav;
+      return 301 https://$host/remote.php/dav;
     }
     location = /.well-known/caldav {
-      return 301 $scheme://$host/remote.php/dav;
+      return 301 https://$host/remote.php/dav;
     }
 
     client_max_body_size 1G;