[9.1](backport #47494) [Filebeat/Journald] Add note about the issues with using globs

[mergify]

Proposed commit message

See title

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
• I have added tests that prove my fix is effective or that my feature works. Where relevant, I have used the stresstest.sh script to run them under stress conditions and race detector to verify their stability.
• I have added an entry in ./changelog/fragments using the changelog tool.

## Disruptive User Impact
## Author's Checklist

How to test this PR locally

Build the docs using docs-builder, then open http://localhost:3000/reference/filebeat/filebeat-input-journald#filebeat-input-journald-paths

Docs preview

• Docs preview

## Related issues
## Use cases
## Screenshots
## Logs

---

This is an automatic backport of pull request #47494 done by Mergify.

[mergify]

Cherry-pick of d7c3735 has failed:

On branch mergify/bp/9.1/pr-47494
Your branch is up to date with 'origin/9.1'.

You are currently cherry-picking commit d7c3735e7.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   docs/reference/filebeat/filebeat-input-journald.md

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[github-actions]

🤖 GitHub comments

Just comment with:

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

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)