fix: remove unused discretization fields

Issue #, if available:

Description of changes:

Testing done:

pip install git+https://github.com/amazon-braket/amazon-braket-sdk-python.git@fix_disc

pip freeze | grep amazon-braket                                                                                                                             
amazon-braket-default-simulator==1.21.6
amazon-braket-schemas==1.21.4
amazon-braket-sdk @ git+https://github.com/amazon-braket/amazon-braket-sdk-python.git@a196dcf0ead48aee5e6f03d987f4ab10c48733b0

Saved the example for MWIS as quera_program.py and ran:

python -m quera_program
>>> python -m quera_program                                                                                                                                                
ARN: arn:aws:braket:us-east-1:<ACCOUNT_ID>:quantum-task/<TASK_UUID>

and verified task creation.

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amazon-braket / amazon-braket-sdk-python