network_traffic: remove invalid value from event.category in SIP sample event

[efd6]

What does this PR do?

This change removes an invalid value in the SIP data set.

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.
• I have verified that Kibana version constraints are current according to guidelines.

Author's Checklist

• [ ]

How to test this PR locally

See #3016 (comment)

Related issues

• Relates network_traffic using invalid ECS values #3329

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• Start Time: 2022-05-13T08:02:45.814+0000

• Duration: 70 min 11 sec

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Name	Metrics % (covered/total)	Diff
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[r00tu53r]

Update PR number xxxx -> 3343

[efd6]

Thanks

[efd6]

This is an incomplete fix since the field values in question originate in packet beat in the SIP plugin. There is a change proposed there to resolve the root issue (should sneak in before the FF).

Significant changes since approval.

[r00tu53r]

LGTM