[AbuseCH] Update typo on base-fields.yml

[P1llus]

What does this PR do?

Updates a typo in base-fields.yml for threat ECS fields

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.

[elasticmachine]

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

[r00tu53r]

LGTM !

[elasticmachine]

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Build stats

• Start Time: 2021-12-13T06:16:15.743+0000

• Duration: 17 min 40 sec

• Commit: 6844843

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Test	Results
Failed	0
Passed	18
Skipped	0
Total	18

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