[v2.7] ci: Specify the exact tag for the new release

[yiannistri]

What this PR does / why we need it:

Specify the exact tag for the new release. This is necessary because by default, goreleaser sorts tags by name before selecting which tag to release, which causes problems when >1 tags point to the same commit (un-rc process). From https://goreleaser.com/cookbooks/set-a-custom-git-tag/

Which issue(s) this PR fixes Issue #596

Special notes for your reviewer:

Checklist:

• [x] squashed commits into logical changes
• [ ] includes documentation
• [ ] adds unit tests
• [ ] adds or updates e2e tests
• [ ] backport needed