[ti_abusech] Change abusech.malwarebazaar.code_sign to Nested field

[legoguy1000]

What does this PR do?

Fixes a field mapping exception with abusech.malwarebazaar.code_sign. Changed the field mapping to Nested from Keyword.

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

• Closes AbuseCH | failed to parse field [abusech.malwarebazaar.code_sign] of type [keyword] #4092

Screenshots

[elasticmachine]

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Build stats

• Start Time: 2022-09-05T23:36:42.252+0000

• Duration: 18 min 47 sec

Test stats 🧪

Test	Results
Failed	0
Passed	23
Skipped	0
Total	23

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

[efd6]

/test

[efd6]

There is probably more to this than just changing the mapping. See elastic/beats#31552.

[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (4/4)	💚
Files	100.0% (4/4)	💚 2.896
Classes	100.0% (4/4)	💚 2.896
Methods	100.0% (51/51)	💚 10.424
Lines	89.636% (493/550)	👎 -2.116
Conditionals	100.0% (0/0)	💚

[efd6]

/test

[legoguy1000]

@efd6 can we rerun tests?

[efd6]

/test

[legoguy1000]

@efd6 GTG??

[efd6]

Thanks