Remove agent field from metric collector

[andsel]

Release notes

[rn:skip]

What does this PR do?

Removed agent field from collector, becuase not used

Why is it important/What is the impact to the user?

Checklist

• My code follows the style guidelines of this project
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
• [ ] I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• [ ]

How to test this PR locally

https://buildkite.com/elastic/logstash-exhaustive-tests-pipeline/builds/2205

Related issues

• Relates Cleanup existing metric code #17891

[github-actions]

🤖 GitHub comments

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Just comment with:

• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)

[mergify]

This pull request does not have a backport label. Could you fix it @andsel? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.
• If no backport is necessary, please add the backport-skip label

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: aaa187b

Failed CI Steps

• :rspec: Ruby unit tests - FIPS mode
• :java: Java unit tests - FIPS mode
• :java: Java unit tests - FIPS mode
• :java: Java unit tests - FIPS mode
• 🥼 Integration Tests - FIPS mode / part 1-of-3
• 🥼 x-pack unit tests - FIPS mode
• 🥼 x-pack integration - FIPS mode

History

• 💛 Build #3215 was flaky c322178

cc @andsel

[jsvd]

LGTM, this was initially introduced by 23dcf46, but logstash-core/lib/logstash/api/lib/app/command.rb no longer exists.