packetbeat/procs: don't log at ERROR for file not found

[efd6]

What does this PR do?

This reduces the logging level of ENOENT errors when attempting to map sockets to processes.

Why is it important?

When processes are short lived this spams the logs with unhelpful log lines.

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
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Author's Checklist

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How to test this PR locally

Related issues

• Fixes Avoid packetbeat flooding logs with FindSocketsOfPid errors when on system with short living processes #33793

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Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

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Build stats

• Start Time: 2022-11-28T23:51:47.375+0000

• Duration: 48 min 46 sec

Test stats 🧪

Test	Results
Failed	0
Passed	1721
Skipped	19
Total	1740

💚 Flaky test report

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