Updated test_atom_arrangement.py

Issue #, if available: fixes #969 Description of changes: test_add_chaining: Verifies the add method supports method chaining. test_iteration: Ensures iteration over AtomArrangement returns the correct coordinates. test_coordinate_list: Validates the coordinate_list method returns the correct coordinate lists. test_discretize: Parametrized test that checks the discretize method for various resolutions. test_invalid_discretization_properties: Expects a DiscretizationError when invalid properties are provided. Testing done: added test

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amazon-braket / amazon-braket-sdk-python