Mark api_key as no_log, since that's supposed to be kept secret

lib/ansible/modules/extras/monitoring/datadog_event.py

@@ -95,7 +95,7 @@ import socket
 def main():
     module = AnsibleModule(
         argument_spec=dict(
-            api_key=dict(required=True),
+            api_key=dict(required=True, no_log=True),
             title=dict(required=True),
             text=dict(required=True),
             date_happened=dict(required=False, default=None, type='int'),