Fix assignment of template field in __init__ in auto_ml.py

[romsharon98]

related: #36484

fix:

CreateAutoMLForecastingTrainingJobOperator's constructor lacks direct assignments for instance members corresponding to the following template fields (i.e., self.field_name = field_name or 
super.__init__(field_name=field_name, ...) ):
['region', 'impersonation_chain', 'parent_model']
CreateAutoMLImageTrainingJobOperator's constructor lacks direct assignments for instance members corresponding to the following template fields (i.e., self.field_name = field_name or 
super.__init__(field_name=field_name, ...) ):
['region', 'impersonation_chain', 'parent_model']
CreateAutoMLTabularTrainingJobOperator's constructor lacks direct assignments for instance members corresponding to the following template fields (i.e., self.field_name = field_name or 
super.__init__(field_name=field_name, ...) ):
['region', 'impersonation_chain', 'parent_model']
CreateAutoMLVideoTrainingJobOperator's constructor lacks direct assignments for instance members corresponding to the following template fields (i.e., self.field_name = field_name or 
super.__init__(field_name=field_name, ...) ):
['region', 'impersonation_chain', 'parent_model']

cc: @shahar1

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