Disabling Chunked Encoding

### What happened?
Currently responses received always have `Transfer-Encoding: chunked`

### What did you expect?
I wish to control this and send complete response.

### Minimal graphql.schema and models to reproduce
Not specific to a schema

### versions
```
go run github.com/99designs/gqlgen version
v0.17.36
go version
go version go1.19.3 darwin/arm64
```