fix: correct S3 bucket owner label key to prevent retrieval errors

[AmitRay9615]

What this PR does / why we need it:

This PR corrects a variable name used to access the S3 bucket owner in the processS3Event function. Currently, labels["bucketOwner"] is used, which results in an error as it should be labels["bucket_owner"] to match the key name in the labels map. This fix ensures that the code correctly retrieves the bucket owner identity from the S3 event, preventing failures during object retrieval.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

This change addresses an error encountered when fetching objects from an S3 bucket due to an incorrect map key reference. The update aligns the variable name with the correct label key.

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• [] Documentation added
• [] Tests updated
• Title matches the required conventional commits format, see here
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• [] Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• [] If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

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[AmitRay9615]

@rafaelroquetto @zerok