JSON parsing error in introspection descriptions

Describe the bug
I'm using a Spring Boot project configured with spring-boot-starter-graphql version 3.5.3, This setup brings in spring-graphql version 1.4.0 and the core graphql-java library version 24.0.

I've found a bug where the introspection query returns a response with invalid JSON. Specifically, the description fields for the built-in __Schema.directives and __Schema.subscriptionType fields are incorrectly formatted. They begin with a single quote (') instead of a double quote ("). This violates the JSON specification and causes parsing errors in many web-based GraphQL clients, such as Hoppscotch.

If this is not a bug and is an intended feature, I apologize. I may have misunderstood its purpose.

If you don't mind, I would be very grateful if you could explain why this is necessary in the code.

Thank you for your time.

To Reproduce
Steps to reproduce the bug:

Set up a Spring Boot GraphQL service using the specified dependencies (spring-graphql 1.4.0 and graphql-java 24.0).
Send a standard introspection query to the service endpoint.

** Introspection query **
The query written below is an introspection query that the Hoppscotch client sends to the GraphQL API server.

    query IntrospectionQuery {
      __schema {
        
        queryType { name kind }
        mutationType { name kind }
        subscriptionType { name kind }
        types {
          ...FullType
        }
        directives {
          name
          description
          
          locations
          args {
            ...InputValue
          }
        }
      }
    }

    fragment FullType on __Type {
      kind
      name
      description
      
      
      fields(includeDeprecated: true) {
        name
        description
        args {
          ...InputValue
        }
        type {
          ...TypeRef
        }
        isDeprecated
        deprecationReason
      }
      inputFields {
        ...InputValue
      }
      interfaces {
        ...TypeRef
      }
      enumValues(includeDeprecated: true) {
        name
        description
        isDeprecated
        deprecationReason
      }
      possibleTypes {
        ...TypeRef
      }
    }

    fragment InputValue on __InputValue {
      name
      description
      type { ...TypeRef }
      defaultValue
      
      
    }

    fragment TypeRef on __Type {
      kind
      name
      ofType {
        kind
        name
        ofType {
          kind
          name
          ofType {
            kind
            name
            ofType {
              kind
              name
              ofType {
                kind
                name
                ofType {
                  kind
                  name
                  ofType {
                    kind
                    name
                    ofType {
                      kind
                      name
                      ofType {
                        kind
                        name
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    }

Expected behavior
The GraphQL response string should be valid JSON and successfully parsed by standard JSON parsers, such as JSON.parse().

Actual behavior
The JSON response contains a specific string (in the description fields) that is not properly formatted. The string begins with a single quote ('), which makes the entire response an invalid JSON string. This causes a parsing error when a client attempts to use a JSON parser like JSON.parse().

The problematic code is located on lines 681 and 685 of the following URL:

.description("'A list of all directives supported by this server.")

.description("'If this server support subscription, the type that subscription operations will be rooted at.")