Currently `ECSOperator` propagates `platform_version` parameter either in case `launch_type` is `FARGATE` or there is `capacity_provider_strategy` parameter provided. The case with `capacity_provider_strategy` is wrong. Capacity provider strategy can contain a reference on EC2 capacity provider. If it's an EC2 capacity provider, then `platform_version` should not be propagated to the `boto3` api call. And it's not possible to do so with the current logic of `ECSOperator` because `platform_version` is always propagated in such case and `boto3` doesn't accept `platform_version` as `None`. So in order to fix that `platform_version` should be an independent parameter and propagated only when it's specified, regardless which `launch_type` or `capacity_provider_strategy` is specified. That should also simplify the logic of `ECSOperator`.

I will prepare a PR to fix that.
tests/providers/amazon/aws/operators/test_ecs.py
assert self.ecs.template_fields == ('overrides',)
    @parameterized.expand(
        [
            ['EC2', None, None, {'launchType': 'EC2'}],
            ['FARGATE', None, None, {'launchType': 'FARGATE', 'platformVersion': 'LATEST'}],
            [
                'EC2',
                None,
                {'testTagKey': 'testTagValue'},
                {'launchType': 'EC2', 'tags': [{'key': 'testTagKey', 'value': 'testTagValue'}]},
            ],
            [
                '',
                None,
                {'testTagKey': 'testTagValue'},
                {'tags': [{'key': 'testTagKey', 'value': 'testTagValue'}]},
            ],
            [
                None,
                {'capacityProvider': 'FARGATE_SPOT'},
                None,
                {
                    'capacityProviderStrategy': {'capacityProvider': 'FARGATE_SPOT'},