fix annotations

[sperlingxx]

1. fix TrainingJobAnnotations func, which crashs trial reconcilement on custom jobs.
2. add omitempty json tag for AlgorithmSpec.AlgorithmSettings

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This change is 

[k8s-ci-robot]

Hi @sperlingxx. Thanks for your PR.

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[gaocegege]

/lgtm
/assign @johnugeorge

[gaocegege]

/ok-to-test

Thanks for your contribution! 🎉 👍

[johnugeorge]

/approve

Thanks 😀

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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