Chore: Update staging.yml

[ekedonald]

Modified the event trigger for the deploy job from push to pull request.

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Modified the event trigger for the deploy job from push to pull request.

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Related Issue (Link to Github issue)

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How Has This Been Tested?

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Screenshots (if appropriate - Postman, etc):

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Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change) ​

  Checklist:

• [x] My code follows the code style of this project.
• [x] I have updated the documentation accordingly.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.