stage: Remove temporary last commit SHA code
stage: Remove temporary last commit SHA code

This commit removes the temporary logic to lookup the last commit
SHA in favor of the function in the release-sdk `git` package.

Signed-off-by: Adolfo García Veytia <9de42c8261a7cacaae239656a4dd6991d9b9250f@uservers.net>

kubernetes/release,kubernetes/release