docs: fix typo

[jochongs]

PR Checklist

Please check if your PR fulfills the following requirements:
fix typo

• 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?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

[coveralls]

Pull Request Test Coverage Report for Build 0250bec8-3a60-45a9-afea-6bd931d115e8

Details

• 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 88.918%

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Totals
Change from base Build bc91b2b9-9bd0-4dac-a3ac-a0d262be1578:	0.0%
Covered Lines:	7197
Relevant Lines:	8094

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💛 - Coveralls