Remove problematic workflow "Remove untagged images"

[kota2and3kan]

Description

This PR removes workflow Remove untagged images.

Remove untagged images uses the GitHub action camargo/delete-untagged-action to remove untagged images. And, the action camargo/delete-untagged-action uses the following GitHub API to get a list of untagged images which will be removed.
https://api.github.com/orgs/scalar-labs/packages/container/scalar-admin-for-kubernetes/versions

On the other hand, now, we push multi-platform images to support several architecture environments.

In the multi-platform image, there are several images/tags in the one image as follows. In this case, there are three tags under the 1.2.0 image. By this configuration, users can pull appropriate images without being aware of both differences based on their environment. (Note: We push these images by using buildx.)

• 1.2.0 (base tag)
  • sha256:xxxx (amd64 image of 1.2.0)
  • sha256:yyyy (amm64 image of 1.2.0)

However, the GitHub API that I mentioned above treats sha256:xxxx and sha256:yyyy as untagged images. So, the action camargo/delete-untagged-action removes these tags.

As a result, the necessary images are removed, and the docker pull command returns the following error.

$ docker pull ghcr.io/scalar-labs/scalar-admin-for-kubernetes:2.0.0-snapshot
2.0.0-snapshot: Pulling from scalar-labs/scalar-admin-for-kubernetes
manifest unknown

To avoid this issue, we have to stop this workflow. So, I just removed it in this PR.

Related issues and/or PRs

N/A

Changes made

• Remove file .github/workflows/remove-untagged-images.yaml.

Checklist

• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation to reflect the changes.
• Any remaining open issues linked to this PR are documented and up-to-date (Jira, GitHub, etc.).
• Tests (unit, integration, etc.) have been added for the changes.
• My changes generate no new warnings.
• Any dependent changes in other PRs have been merged and published.

Additional notes (optional)

If we remove this workflow, a lot of untagged images remain in the GitHub Packages. So, we have to consider to another way to remove appropriate untagged images.

[feeblefakie]

LGMT! Thank you!

[supl]

LGTM.
Thank you!