fix: update broken link in SetMetadata decorator documentation

[tomaszwysocki]

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:
  Documentation

What is the current behavior?

The current behavior is that the link in the SetMetadata decorator documentation is broken and redirects to the wrong page.

What is the new behavior?

The new behavior is that the broken link in the SetMetadata decorator documentation has been fixed to accurately direct users to the Reflection section within the Execution Context page of the NestJS fundamentals documentation.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[coveralls]

Pull Request Test Coverage Report for Build 0a9caa66-0c45-437d-9820-806735b64eb9

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 92.146%

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Totals
Change from base Build fad5078e-9529-46ad-977e-491c6acb241f:	0.0%
Covered Lines:	6734
Relevant Lines:	7308

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💛 - Coveralls

[kamilmysliwiec]

LGTM