bugfix: no __contains__ on StrEnum until 3.12

[wssheldon]

Even if you implement __contains__ you still get the following error:

<stdin>:1: DeprecationWarning: in 3.12 __contains__ will no longer raise TypeError, but will return True or
False depending on whether the value is a member or the value of a member
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/wshel/.pyenv/versions/3.11.2/lib/python3.11/enum.py", line 745, in __contains__
    raise TypeError(
TypeError: unsupported operand type(s) for 'in': 'str' and 'EnumType'

    def __contains__(self, other):
        """
        Returns True if self has at least the same flags set as other.
        """
        if not isinstance(other, self.__class__):
            raise TypeError(
                "unsupported operand type(s) for 'in': %r and %r" % (
                    type(other).__qualname__, self.__class__.__qualname__))
        return other._value_ & self._value_ == other._value_

(dispatch) wshel@wills-mbp dispatch % python3 
Python 3.11.2 (main, Mar  6 2023, 17:43:14) [Clang 14.0.0 (clang-1400.0.29.202)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from dispatch.enums import DispatchEnum
>>> from dispatch.plugins.dispatch_slack.enums import SlackAPIErrorCode
>>> slack_error = "this_is_retryable"
>>> slack_error not in SlackAPIErrorCode
<stdin>:1: DeprecationWarning: in 3.12 __contains__ will no longer raise TypeError, but will return True or
False depending on whether the value is a member or the value of a member
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/wshel/.pyenv/versions/3.11.2/lib/python3.11/enum.py", line 745, in __contains__
    raise TypeError(
TypeError: unsupported operand type(s) for 'in': 'str' and 'EnumType'
>>> exit()



(dispatch) wshel@wills-mbp dispatch % python3
Python 3.11.2 (main, Mar  6 2023, 17:43:14) [Clang 14.0.0 (clang-1400.0.29.202)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from dispatch.plugins.dispatch_slack.enums import SlackAPIErrorCode
>>> exit()
(dispatch) wshel@wills-mbp dispatch % python3
Python 3.11.2 (main, Mar  6 2023, 17:43:14) [Clang 14.0.0 (clang-1400.0.29.202)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from dispatch.plugins.dispatch_slack.enums import SlackAPIErrorCode
>>> slack_error = "this_is_retryable"
>>> slack_error not in SlackAPIErrorCode
<stdin>:1: DeprecationWarning: in 3.12 __contains__ will no longer raise TypeError, but will return True or
False depending on whether the value is a member or the value of a member
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/wshel/.pyenv/versions/3.11.2/lib/python3.11/enum.py", line 745, in __contains__
    raise TypeError(
TypeError: unsupported operand type(s) for 'in': 'str' and 'EnumType'
>>> slack_error not in SlackAPIErrorCode.__members__.values()
True