Drop unused post_submit_commands copy from SparkSubmitOperator init

[1fanwang]

post_submit_commands is a template field, so it is rendered after __init__ runs. The constructor also kept a private self._post_submit_commands = list(post_submit_commands) if post_submit_commands else [], built from the un-rendered value. Nothing reads that copy: the operator forwards the rendered self.post_submit_commands to SparkSubmitHook, which builds its own list and runs the commands. Removing it stops the constructor reading the template field and clears its validate-operators-init exemption.

related: #70296

Testing Done

validate_operators_init.py on the operator, before (with the exemption removed):

SparkSubmitOperator's constructor applies logic to template fields. Template fields are
rendered after the constructor runs, so validation or transformation here acts on the
un-rendered Jinja expression and should move to execute():
  line 266: self._post_submit_commands = list(post_submit_commands) if post_submit_commands else []  (post_submit_commands)

After removing the line, the validator exits 0.

test_spark_submit.py (operator suite): 69 passed. The removed attribute had no readers, so behaviour is unchanged.

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[shahar1]

Nice catch!

[github-actions]

Backport failed to create: v3-3-test. View the failure log Run details

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Status	Branch	Result
❌	v3-3-test

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After you have resolved the conflicts, you can continue the backport process by running:

cherry_picker --continue

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