fix: pin skaffold version and change installation method

[f1ames]

This PR pins skaffold to previous version (2.9.0) because it started failing with latest one (2.10.0), for example: https://github.com/kubeshop/monokle-admission-controller/actions/runs/7569302057/job/20612383533#step:7:18.

Changes

• As above.

Fixes

• As above.

Checklist

• [ ] tested locally
• [ ] added new dependencies
• [ ] updated the docs
• [ ] added a test

[f1ames]

Merging since this is quite minor change.