docs(cqrs): fix property typo in QueryHandler example

[VictorOluwaseun]

PR Checklist

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• The commit message follows our guidelines: https://github.com/nestjs/docs.nestjs.com/blob/master/CONTRIBUTING.md

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
• Docs
• Other... Please describe:

What is the current behavior?

In the CQRS → Queries example, the GetHeroHandler incorrectly uses query.hero,
even though the GetHeroQuery class defines the property as heroId.
This causes an inconsistency in the example code and may confuse readers following the docs.

What is the new behavior?

The example has been corrected to use query.heroId, matching the property defined in the GetHeroQuery class.

Does this PR introduce a breaking change?

• Yes
• No

Other information