text: Title: [FEATURE] Negative tests for GraphQL
  Body: ### Checklist
  
  - [x] I checked the [FAQ section](https://schemathesis.readthedocs.io/en/stable/faq.html#frequently-asked-questions) of the documentation
  - [x] I looked for similar issues in the [issue tracker](https://github.com/schemathesis/schemathesis/issues)
  - [x] I am using the latest version of Schemathesis
  
  ### Describe the bug
  
  I try to generate negative tests, however it doesn't work.
  
  ### To Reproduce
  
  ```python
  
  import schemathesis
  from hypothesis import settings
  from schemathesis import DataGenerationMethod
  
  f = open("schema.graphql")
  schema = schemathesis.graphql.from_file(f, data_generation_methods=[DataGenerationMethod.negative])
  
  
  @schema.parametrize()
  @settings(max_examples=10)
  def test_api(case):
      print(case.body)
  
  ```
  
  Minimal API schema causing this issue:
  
  ```
  schema {
      query: Query
      mutation: Mutation
  }
  
  type Query {
      hello: String
      user(id: Int!): String
  }
  
  type Mutation {
      createUser(name: String!, age: Int!): String
  }
  
  ```
  
  ### Expected behavior
  
  I was expecting negative tests, but clearly these are just ordinary.
  ```
  {
    user(id: 0)
  }
  ```
  
  ```
  mutation {
    createUser(name: "", age: 0) {
      age
    }
  }
  ```
  
  ### Environment
  
  ```
  - OS: MacOS Ventura
  - Python version: 3.12
  - Schemathesis version: 3.32.2
  ```
  