Convert "container cleanup" log message from INFO to DEBUG type

[Pexers]

Just as described in #996, converting the bellow log message from INFO to DEBUG type will prevent it from being logged every 5 minutes on the Jenkins logs.

Jul 30, 2023 12:48:31 PM INFO com.nirima.jenkins.plugins.docker.DockerContainerWatchdog processCloud
Will not cleanup superfluous containers on DockerCloud [name=docker, dockerURI=unix:///var/run/docker.sock], as it is disabled
Jul 30, 2023 12:53:31 PM INFO com.nirima.jenkins.plugins.docker.DockerContainerWatchdog processCloud
Will not cleanup superfluous containers on DockerCloud [name=docker, dockerURI=unix:///var/run/docker.sock], as it is disabled
...

This message generates unnecessary noise, thus potentially obscuring developers from reading other logs with higher importance.

Testing done

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[MarkEWaite]

Thanks!