fix(ci): remove unnecessary apko install

[emosbaugh]

What this PR does / why we need it:

Apko is no longer needed as image is now built in a container.

Which issue(s) this PR fixes:

Does this PR require a test?

Does this PR require a release note?

Does this PR require documentation?

[github-actions]

This PR has been released (on staging) and is available for download with a embedded-cluster-smoke-test-staging-app license ID.

Online Installer:

curl "https://staging.replicated.app/embedded/embedded-cluster-smoke-test-staging-app/ci/appver-dev-660b2f5" -H "Authorization: $EC_SMOKE_TEST_LICENSE_ID" -o embedded-cluster-smoke-test-staging-app-ci.tgz

Airgap Installer (may take a few minutes before the airgap bundle is built):

curl "https://staging.replicated.app/embedded/embedded-cluster-smoke-test-staging-app/ci-airgap/appver-dev-660b2f5?airgap=true" -H "Authorization: $EC_SMOKE_TEST_LICENSE_ID" -o embedded-cluster-smoke-test-staging-app-ci.tgz

Happy debugging!

[emosbaugh]

Merging through the flake