System.Text.Json.JsonException when parsing response from SendMutationAsync.

We have recently upgraded our project to .Net 7 and we have started seeing this issue. We are using version 6.0.2.
but the json response looked fine.
Response:
{"data":{"provisionSsoUser":{"user":{"id":"d48656b8-c5a2-42f4-be2b-62f5e647c90f"}}}}

### Code as below:
```
var client = new GraphQLHttpClient(
x =>
{
x.EndPoint = _graphQlEndpoint;
x.HttpMessageHandler = new LoggingHandler(new HttpClientHandler());
},
new DebugSerializer());
client.HttpClient.DefaultRequestHeaders.Add("Authorization", $"PSK {_graphQlPsk}");

var provisionSsoUserRequest = new GraphQLRequest
{
Query = GraphQl.ProvisionSsoUser,
OperationName = "ProvisionSsoUser",
Variables = new { input = new { email = "test@test.com", name = "FullName", cw1OrganizationCode = "Code" } }
};

// Exception thrown at this line.
var response = await client.SendMutationAsync(provisionSsoUserRequest, () => new { provisionSsoUser = new { user = new { id = Guid.Empty } } });
```

### StackTrace as below:

System.Text.Json.JsonException: The converter 'GraphQL.Client.Serializer.SystemTextJson.ImmutableConverter' read too much or not enough. Path: $ | LineNumber: 0 | BytePositionInLine: 9.
at System.Text.Json.ThrowHelper.ThrowJsonException_SerializationConverterRead(JsonConverter converter)
at System.Text.Json.Serialization.JsonConverter`1.VerifyRead(JsonTokenType tokenType, Int32 depth, Int64 bytesConsumed, Boolean isValueConverter, Utf8JsonReader& reader)
at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
at System.Text.Json.Serialization.JsonConverter`1.ReadCoreAsObject(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
at System.Text.Json.JsonSerializer.ReadCore[TValue](Utf8JsonReader& reader, JsonTypeInfo jsonTypeInfo, ReadStack& state)
at System.Text.Json.JsonSerializer.Read[TValue](Utf8JsonReader& reader, JsonTypeInfo jsonTypeInfo)
at GraphQL.Client.Serializer.SystemTextJson.ImmutableConverter.Read(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options) in /_/src/GraphQL.Client.Serializer.SystemTextJson/ImmutableConverter.cs:line 68
at System.Text.Json.Serialization.Converters.CastingConverter`2.Read(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options)
at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.ReadJsonAndSetMember(Object obj, ReadStack& state, Utf8JsonReader& reader)
at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
at System.Text.Json.JsonSerializer.ContinueDeserialize[TValue](ReadBufferState& bufferState, JsonReaderState& jsonReaderState, ReadStack& readStack, JsonTypeInfo jsonTypeInfo)
at System.Text.Json.JsonSerializer.ReadFromStreamAsync[TValue](Stream utf8Json, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
at GraphQL.Client.Http.GraphQLHttpClient.SendHttpRequestAsync[TResponse](GraphQLRequest request, CancellationToken cancellationToken) in /_/src/GraphQL.Client/GraphQLHttpClient.cs:line 129
at GraphQL.Client.Http.GraphQLHttpClient.SendQueryAsync[TResponse](GraphQLRequest request, CancellationToken cancellationToken) in /_/src/GraphQL.Client/GraphQLHttpClient.cs:line 81