Update unit tests for RHOAI ray image

[ChughShilpa]

Issue link

https://issues.redhat.com/browse/RHOAIENG-10011

What changes have been made

With the new UBI9 based ray runtime image quay.io/rhoai/ray:2.23.0-py39-cu121 used as default in codeflare-sdk raycluster-configuration, updating unit tests in codeflare-sdk for RHOAI Ray runtime container image

• Modify existing unit tests to verify that default Ray image is used when user doesn't specify specific Ray image when creating ray cluster resource
• Add a unit test to verify that custom image is used when user specify a custom image when creating ray cluster resource

Verification steps

Checks

• I've made sure the tests are passing.
• Testing Strategy
  • Unit tests
  • Manual tests
  • Testing is not required for this change

[Bobbins228]

/lgtm

[Bobbins228]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Bobbins228, sutaakar

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