remove nginx error pages for nextcloud (#1141)

They are known to cause troubles, for more information see
https://github.com/nextcloud/server/issues/3847

conf/nginx-primaryonly.conf

@@ -41,8 +41,6 @@
 		fastcgi_param MOD_X_ACCEL_REDIRECT_PREFIX /owncloud-xaccel;
 		fastcgi_read_timeout 630;
 		fastcgi_pass php-fpm;
-		error_page 403 /cloud/core/templates/403.php;
-		error_page 404 /cloud/core/templates/404.php;
 		client_max_body_size 1G;
 		fastcgi_buffers 64 4K;
 	}