update-json-specs.yml: add container_metadata_discovery.json

[v1v]

What does this pull request do?

Update the updatecli pipeline for the automation regarding the json specs.

Why is it important?

container_metadata_discovery.json is a new file while cgroup_parsing.json has been removed.

Otherwise the automation fails

https://github.com/elastic/apm-agent-ruby/actions/runs/5817528861/job/15772319674#step:3:2142

Checklist

• I have signed the Contributor License Agreement.
• My code follows the style guidelines of this project (See .rubocop.yml)
• I have rebased my changes on top of the latest main branch

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

• I have made corresponding changes to the documentation
• I have updated CHANGELOG.asciidoc
• I have updated supported-technologies.asciidoc
• Added an API method or config option? Document in which version this will be introduced

Related issues

• Relates Modify spec for cgroups v2 container ID parsing apm#807