Fix region parameter in EKS operators/sensors

[vincbeck]

#48192 introduced a bug in EksClusterStateSensor. region is specified in the list of templated fields but not saved as attribute which causes:

[2025-04-11 17:18:06,028] {taskinstance.py:2948} ERROR - Task failed with exception
Traceback (most recent call last):
  File "/opt/airflow/task-sdk/src/airflow/sdk/definitions/_internal/abstractoperator.py", line 353, in _do_render_template_fields
    value = getattr(parent, attr_name)
AttributeError: 'EksClusterStateSensor' object has no attribute 'region'

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[o-nikolas]

Yeah, we should have run the system tests on that previous PR :/