Fix parsing of apache trace log levels

[jsoriano]

What does this PR do?

Fix parsing of apache trace log levels, solves elastic/beats#28650 in the Apache integration.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• If I'm introducing a new feature, I have modified the Kibana version constraint in my package's manifest.yml file to point to the latest Elastic stack release (e.g. ^7.13.0).

Related issues

• Relates [Filebeat] filebeat-7.15.0-apache-error-pipeline doesn't recognize apache trace log levels beats#28650
• Fix for beats in Fix parsing of apache trace log levels beats#28717

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Pinging @elastic/integrations (Team:Integrations)

[elasticmachine]

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