refactor: Remove priority classes from executor CR

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Pull Request Template

Description

Now that the Armada preemption behavior has been clarified we know that preemption happens in the scheduler and not the k8s layer. As such we don't need k8s priority classes to be configured.

Fixes # (issue)

Type of change

Please select the type of change your PR introduces:

• Bugfix
• Feature
• Code Style Update (formatting, renaming)
• Refactor (code changes that do not fix a bug or add a feature)
• Documentation Update
• Other (please describe):

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions to reproduce these tests. List any relevant details for your test configuration.

• Test Configuration:

  • Kubernetes Version:
  • Helm Version:
  • OS:

• Test Steps:

  1. Step 1
  2. Step 2
  3. ...

Checklist:

• My code follows the style guidelines of this project.
• I have performed a self-review of my code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• Any dependent changes have been merged and published in downstream modules.