Update playbook.json example code for bat_signal message_template - country_name

[Ben Pruce]

"message_template": "`{context.artifacts.event.details.username}` logged in from `{context.results.Geolocate_IP.country_name}` at coordinates `{context.results.Geolocate_IP.latitude}`, `{context.results.Geolocate_IP.longitude}`"

should be

"message_template": "`{context.artifacts.event.details.username}` logged in from `{context.results.Geolocate_IP.country}` at coordinates `{context.results.Geolocate_IP.latitude}`, `{context.results.Geolocate_IP.longitude}`"