fix: add missing omitempty tags in the AuthPodIdentity struct

[alxndr13]

Added missing omitempty json tags in the AuthPodIdentity struct

Checklist

• When introducing a new scaler, I agree with the scaling governance policy
• I have verified that my change is according to the deprecations & breaking changes policy
• Tests have been added
• Changelog has been updated and is aligned with our changelog requirements
• A PR is opened to update our Helm chart (repo) (if applicable, ie. when deployment manifests are modified)
• A PR is opened to update the documentation on (repo) (if applicable)
• Commits are signed with Developer Certificate of Origin (DCO - learn more)

Fixes #6779

[JorTurFer]

Could you rebase your PR to solve the conflict and generate the manifests?

[alxndr13]

@JorTurFer done ✅

ran make generate if that's what you meant. it didn't create a change though.

[JorTurFer]

/run-e2e internal
Update: You can check the progress here