Change the default image for the new Katib UI

[andreyvelich]

Related: #1597.

As we discussed, for Kubeflow 1.4 in the default Katib manifests we will use the new Katib UI image.
We still need to make some changes in the website docs: #1595 before the release.

I modified Katib README, please take a look.

/assign @kimwnasptd @gaocegege @johnugeorge

/hold for the review.

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[andreyvelich]

We should decide which image we are going to use for the new Katib UI.
Maybe we can re-use docker.io/kubeflowkatib/katib-ui and users can deploy docker.io/kubeflowkatib/katib-ui:v0.11.1 for the previous UI.
Currently, AWS Test infra has only docker.io/kubeflowkatib/katib-ui image: https://github.com/kubeflow/testing/blob/master/aws/IaC/CDK/test-infra/config/static_config/ECR_Resources.py#L13.

/hold

[gaocegege]

docker.io/kubeflowkatib/katib-ui SGTM

[johnugeorge]

SGTM

[andreyvelich]

I am using docker.io/kubeflowkatib/katib-ui for the new UI.
@gaocegege @kimwnasptd @johnugeorge Please take a look.

/hold cancel

[andreyvelich]

/retest

[andreyvelich]

Tests are passed, @kimwnasptd @gaocegege @johnugeorge if you are fine with the changes let's merge it.

[gaocegege]

/lgtm