Remove colorize_messages setting
This doesn't seem to be used, so just remove it.
@@ -3122,7 +3122,6 @@ class PluginConfig(object):
# extracted.
# TODO: setting descriptions.
settings = {
- 'colorize_messages': 'false',
'colorize_private_chats': 'false',
'debug_mode': 'false',
'debug_level': '3',
