Install latest pipeline release in tests

[piyush-garg]

This will make sure we are installing latest
pipeline release instead of the first tag on releases

This will fix the e2e tests failures observed in
#1754 with error message
like json: unknown field "artifacts"

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• Has Tests included if any functionality added or changed
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Release Notes

Install latest pipeline release in tests

[khrm]

/lgtm

[tekton-robot]

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[savitaashture]

/lgtm