Change fields as decorator documentation for endpoint definitions

[smholloway]

See: https://django-declarative-apis.readthedocs.io/en/latest/fields.html#field-as-decorators-on-a-function

The example for this shows:

@field(
     required=False,
     name='completion_status',
     type=bool,
     default=None,
     description='Status for a task in the todo list. The only valid status is "True"')
 def status(self, raw_value):
    if status.get(raw_value, None) != True:
         raise ValueError(f"{raw_value} is not a valid status")
    return True

But in this example, what exactly is status? I think this should just be if raw_value != True