Refactor: Attribute.class used instead of helper methods in PythonSer… (#1475)

* Refactor: Attribute.class used instead of helper methods in PythonServerAttributeUtils

Helper methods in PythonServerAttributeUtils have been deprecated in favor of using Attribute.class directly

Co-authored-by: Matteo Bigoi <1781140+crisidev@users.noreply.github.com>

* Smithy Python: PyException removed from enum

Smithy enums do not have ErrorTrait so there is no need to check and generate code for pyo3::exceptions::PyException

Co-authored-by: Fahad Zubair <fahadzub@amazon.com>
Co-authored-by: Matteo Bigoi <1781140+crisidev@users.noreply.github.com>