2i2c-aws-us, cosmicds: cleanup not needed trick for repo2docker logs

[consideRatio]

I've confirmed that this isn't needed, practically checking that I get logs at /srv/repo/.jupyter-server-log.txt even when we leave singleuser.cmd set to jupyterhub-singleuser, which overrides the docker image's CMD (but not ENTRYPOINT).

repo2docker sets ENTRYPOINT (k8s command) and CMD (k8s args, and singleuser.cmd mapping to KubeSpawner.cmd) like this, as seen from docker inspect quay.io/nmearl/hubble-user-image:294205fdd286:

            "Cmd": [
                "jupyter",
                "notebook",
                "--ip",
                "0.0.0.0"
            ],

            "Entrypoint": [
                "/usr/local/bin/repo2docker-entrypoint"
            ],

With this, #3805, and #3797, we no longer set cmd explicitly for any community, and rely systematically on the z2jh defaults of specifying singleuser.cmd. In practice, images ENTRYPOINT are systematically untouched, and images CMD are systematically replaced with jupyterhub-singleuser.

[github-actions]

Merging this PR will trigger the following deployment actions.

Support and Staging deployments

Cloud Provider	Cluster Name	Upgrade Support?	Reason for Support Redeploy	Upgrade Staging?	Reason for Staging Redeploy
aws	2i2c-aws-us	No		Yes	Following prod hubs require redeploy: cosmicds

Production deployments

Cloud Provider	Cluster Name	Hub Name	Reason for Redeploy
aws	2i2c-aws-us	cosmicds	Following helm chart values files were modified: cosmicds.values.yaml

[consideRatio]

Thank you @sgibson91 for reviewing!

[github-actions]

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Monitor the deployment of the hubs here 👉 https://github.com/2i2c-org/infrastructure/actions/runs/8325206274