fix(parser): Removed the nullable type from the md5OfMessageAttributes in SqsRecordSchema

[sdangol]

Summary

This PR removes the nullable type from the md5OfMessageAttributes in the SqsRecordSchema aligning with the @types/aws-lambda package

Changes

1. Removed the nullable type from the md5OfMessageAttributes property in the SqsRecordSchema
2. Updated the data in firehose-sqs.json test event to remove the null value of md5OfMessageAttributes

Issue number: #4109

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[boring-cyborg]

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[dreamorosi]

Great work, thank you for fixing the schema and congrats for your first PR merged in this project 🎉

[boring-cyborg]

Awesome work, congrats on your first merged pull request and thank you for helping improve everyone's experience!