Fix domain name in slack module

library/notification/slack

@@ -50,7 +50,7 @@ options:
     default: ansible
   icon_url:
     description:
-      - Url for the message sender's icon (default C(http://www.ansibleworks.com/favicon.ico))
+      - Url for the message sender's icon (default C(http://www.ansible.com/favicon.ico))
     required: false
   icon_emoji:
     description:
@@ -143,7 +143,7 @@ def main():
             msg         = dict(type='str', required=True),
             channel     = dict(type='str', default=None),
             username    = dict(type='str', default='Ansible'),
-            icon_url    = dict(type='str', default='http://www.ansibleworks.com/favicon.ico'),
+            icon_url    = dict(type='str', default='http://www.ansible.com/favicon.ico'),
             icon_emoji  = dict(type='str', default=None),
             link_names  = dict(type='int', default=1, choices=[0,1]),
             parse       = dict(type='str', default=None, choices=['none', 'full']),