Add Changelog for Training Operator v1.8.0-rc.0 #1111

Job	Run time
Publish Image (kubectl-delivery, build/images/kubectl-delivery/Dockerfile, linux/amd64,linux/arm6... / Publish Image	1m 9s
Publish Image (storage-initializer, sdk/python/kubeflow/storage_initializer/Dockerfile, sdk/pytho... / Publish Image	11m 10s
Publish Image (trainer-huggingface, sdk/python/kubeflow/trainer/Dockerfile, sdk/python/kubeflow/t... / Publish Image	10m 49s
Publish Image (training-operator, build/images/training-operator/Dockerfile, linux/amd64,linux/ar... / Publish Image	24m 48s
	47m 56s

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