Fix country()/countryCode() mixup in example Lua Record

Fix country()/countryCode() mixup in example Lua Record

The country() function returns true if the country code for the query source IP address matches the country code passed to the function.
The countryCode() function doesn't take any arguments and just returns the country code of the query source IP address.

For this example, we're checking if the country for the query source IP address is "US" and expecting a true/false response, so country() is the correct function to use.
Alternatively, this would be something like "if countryCode() == 'US' then return...".