fix enum type assertion with python versions less than 3.12

[dansola]

Why are the changes needed?

Follow up on: #2845

Python versions less than 3.12 don't support using in with an Enum (link).

Changed in version 3.12: Before Python 3.12, a TypeError is raised if a non-Enum-member is used in a containment check.

As a result, the linked previous PR results in a Reason unsupported operand type(s) for 'in': 'str' and 'EnumType' error.

What changes were proposed in this pull request?

Rather than checking the python version, just convert the enum items to a list and use in from there.

How was this patch tested?

from enum import Enum

from flytekit import task, workflow


class Color(Enum):
    RED = 'red'
    GREEN = 'green'
    BLUE = 'blue'

@task
def my_task(c: Color) -> Color:
    print(c)
    return c


@workflow
def wf(c: Color) -> Color:
    return my_task(c=c)

union run wf.py wf --c red

Success with python 3.12 but error with python 3.11.

flyteorg/flyte#5904

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

Related PRs

#2845

[wild-endeavor]

Thanks!