fix(microservices): Update LogEntry in external kafka interface

[Wojciechowski-Marcin]

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• 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?

Current interface is from version 1.15.0 of kafkajs or earlier, which resulted in a typescript error in my project
Starting version 1.16.0 of kafkajs this field is changed from type Date to string

Type 'import("<path>/node_modules/@nestjs/microservices/external/kafka.interface").LogEntry' is not assignable to type 'import("<path>/node_modules/kafkajs/types/index").LogEntry'.
          The types of 'log.timestamp' are incompatible between these types.
            Type 'Date' is not assignable to type 'string'.

Issue Number: N/A

What is the new behavior?

Interface has been updated and the problem doesn't occur anymore
Link to new interface in kafka
Tested on kafkajs version v1.16.0

Does this PR introduce a breaking change?

• Yes
• No

Possible breaking change for apps using older Kafka versions <=1.15.0

[coveralls]

Pull Request Test Coverage Report for Build 69da6f99-e686-4f42-8345-4c56b17c04f8

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

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Totals
Change from base Build decd974f-5945-46a6-bbca-7cb621f03b85:	0.0%
Covered Lines:	0
Relevant Lines:	0

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💛 - Coveralls

[micalevisk]

I believe this introduces breaking changes as LoggerEntryContent is public

[kamilmysliwiec]

lgtm