Update sdk release to 1.2.1

[Tomcli]

Which issue is resolved by this Pull Request:
Resolves #

Description of your changes:
Update SDK release to 1.2.1 to address some of the recent bugs we have fixed for resource op and loops. No changes on the backend and deployment side.

Environment tested:

• Python Version (use python --version):
• Tekton Version (use tkn version):
• Kubernetes Version (use kubectl version):
• OS (e.g. from /etc/os-release):

Checklist:

• The title for your pull request (PR) should follow our title convention. Learn more about the pull request title convention used in this repository.

[Tomcli]

/cc @yhwang

[yhwang]

/lgtm

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Tomcli, yhwang

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[yhwang]

@Tomcli I believe I added all changes in this column: https://github.com/kubeflow/kfp-tekton/projects/2#column-18511595
hope the content there should be accurate.