mimecast/auditevents: fix typo

[efd6]

What does this PR do?

This fixes a documentation bug.

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

Related issues

• Relates fields yaml files typos #2643

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• Start Time: 2022-02-07T09:25:43.160+0000

• Duration: 29 min 38 sec

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Test	Results
Failed	0
Passed	61
Skipped	0
Total	61

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