updatecli: ruby manifest fails often due to DockerHub rate limit

[dduportal]

Updatecli tracks the latest available version of Ruby with the manifest https://github.com/jenkins-infra/packer-images/blob/42616f9f7cb4e7399608f6e568c834ef1b5fea14/updatecli/updatecli.d/ruby.yml.

This manifest fails quite often since beginning of April with the following error:

ERROR: ✗ GET https://index.docker.io/v2/library/ruby/manifests/3.4.3: TOOMANYREQUESTS: You have reached your unauthenticated pull rate limit. https://www.docker.com/increase-rate-limit

It's due to using a source of type "Docker Image" without being authenticated on the DockerHub:

packer-images/updatecli/updatecli.d/ruby.yml

Lines 17 to 28 in 42616f9

	# Use kind: dockerimage instead of kind: githubRelease until https://github.com/updatecli/updatecli/issues/1951 is fixed
	rubyDockerImageLatestVersion:
	kind: dockerimage
	name: "Get the latest Ruby version"
	spec:
	image: "ruby"
	tagfilter: >-
	\d\.\d\.\d$
	versionfilter:
	kind: regex
	pattern: >-
	\d\.\d\.\d$