Change Commit Checker to get the PR last commit

[rimolive]

Description of your changes:

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.

[DharmitD]

I would suggest adding a step to include fetch-depth: 0 here, to fetch all history for all branches and tags.

[DharmitD]

or a git fetch --all

[HumairAK]

I don't think we need all branch history for this, we're just comparing main branch with the pr sha commit

[HumairAK]

/lgtm
/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: HumairAK

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[dsp-developers]

Commit Checker results:
==== These are the results of the commit checker scans ====
==== If these are not commits from upstream kfp, then ====
==== please ensure you adhere to the commit checker formatting ====
$(podman run -q -v /home/runner/work/data-science-pipelines/data-science-pipelines:/src/app-root quay.io/rmartine/commitchecker:latest --start 7127a61 --end 47fb475)