Fix schema definition for federation 2 @link in schema-first

[burn2delete]

Update graphql-federation-definitions.factory.ts

PR Checklist

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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?

schema definition and use of @link is not included in the SDL for the schema in schema-first approach

Issue Number: N/A

What is the new behavior?

schema definition and use of @link is properly included in the SDL for the subgraph

Does this PR introduce a breaking change?

• Yes
• No

Other information