refactor(microservices): change isNotKafkaMessage validation condition

[jochongs]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

If either key or value is included in the object, it will be treated as a Kafka message.

Issue Number: #12886

What is the new behavior?

Objects containing both key and value attributes will be treated as Kafka messages.

Does this PR introduce a breaking change?

• Yes
• No

Other information

If concerns about breaking changes arise, it might be necessary to utilize an options object.

[coveralls]

Pull Request Test Coverage Report for Build e841d23b-c7bc-498f-9e0c-cfad07a98ab4

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.123%

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Totals
Change from base Build eacd3e56-4bed-4f5e-9bab-412a10335aab:	0.0%
Covered Lines:	6736
Relevant Lines:	7312

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💛 - Coveralls