Lower floor for kfp-tekton dependency

[ptitzler]

Lower floor for kfp-tekton dependency to version 1.5.2 to re-establish compatibility with older versions of Tekton. Since version 1.6+ includes breaking API changes (v1beta1 -> v1), users will have to manually choose the kfp-tekton package version that is compatible with the Tekton version that's installed on the server.

What changes were proposed in this pull request?

• Lower kfp-tekton dependency to support older releases of Tekton.

How was this pull request tested?

• pip installed kfp-tekton 1.5.2
• pip installed Elyra
• confirmed that Elyra can submit a pipeline on a cluster where Tekton Pipelines v0.33.2 is deployed

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[kevin-bates]

Thanks @ptitzler.