[8.13](backport #39713) [x-pack/filebeat/cel] increase timeout in unit-tests

[mergify]

Proposed commit message

As captured here there have been seldom occurrences that unit-tests of cel input come up with failures. After a quick analysis and a discussion with @efd6, we both agree that the context timeout in the cel unit-tests can end up being too tight, especially for machines under workload, and hence this PR increases it. Note that this timeout increment shouldn't affect the duration of the passing unit-tests as the context is cancelled as soon as the defined criteria are met.

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.

Disruptive User Impact

Author's Checklist

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How to test this PR locally

Related issues

• Closes x-pack/filebeat/input/cel TestInput/retry_failure on Windows #39657

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This is an automatic backport of pull request #39713 done by Mergify.

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