UID2-7920: Normalize shared actions workflow casing

[swibi-ttd]

Summary

• normalize all uid2-shared-actions references in the Docker release workflow to IABTechLab casing
• align the release workflow with the certificate identity policy used by attestation verification
• keep the shared attestation trust policy unchanged

Verification

• parsed release-all-docker-images.yaml successfully
• actionlint passed
• confirmed all 15 shared-action references use IABTechLab casing
• git diff --check passed

Evidence

• Failing release: https://github.com/IABTechLab/uid2-examples/actions/runs/35563729206
• Jira: https://thetradedesk.atlassian.net/browse/UID2-7920