chore: Update model serving incubation branches (manifests)

[israel-hdez]

Description

• ModelMesh new incubation branch is now release-v0.12.0-rc0
• KServe new incubation branch is now release-v0.12.1.

How Has This Been Tested?

Running the modified script manually and ensuring it downloads the manifests correctly.

Merge criteria:

• The commits are squashed in a cohesive manner and have meaningful messages.
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cam-garrison, ykaliuta

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[VaishnaviHire]

Hi @israel-hdez , we saw consecutive test failures for Kserve, any changes in kserve manifests with new version?

[israel-hdez]

/retest

@VaishnaviHire There were some missing container tags. I fixed.
I hope this now passes.