fix: Cleanup load balancers in spark operator cleanup

[alanty]

What does this PR do?

Adds commands to the cleanup.sh script in the spark operator blueprint to ensure the load balancer and related resources created for the Nginx ingress controller are deleted. This avoids problems deleting the VPC, resolving #741

I used the same commands found in the nvidia-triton-server blueprint.

Motivation

cleaning up this blueprint was inconsistent,

More

• Yes, I have tested the PR using my local account setup (Provide any test evidence report under Additional Notes)
• Mandatory for new blueprints. Yes, I have added a example to support my blueprint PR
• Mandatory for new blueprints. Yes, I have updated the website/docs or website/blog section for this feature
• Yes, I ran pre-commit run -a with this PR. Link for installing pre-commit locally

For Moderators

• E2E Test successfully complete before merge?

Additional Notes