Federation does not honor extend on `type Query` when introspecting

### What happened?

After running generate and running the service, I use introspection (`rover graph introspect http://localhost:8888/query`) to generate a schema.gql (SDL). The output for `type Query{}` does not carry over the extend prefix from the schema. My Apollo federated server will not resolve queries to my subgraph unless the Query type is extended. Is this a bug or is there an alternate way to generate a Federated SDL?

### What did you expect?

Introspected SDL should contain `extend type Query {` instead of `type Query {`

### Minimal graphql.schema and models to reproduce

```
type CheckIssue {id: Int}

extend type Query {
issue: CheckIssue!
}
```

### versions
- `go run github.com/99designs/gqlgen version` v0.17.22
- `go version` 1.19.4 darwin/arm64