WriteGetObjectResponseRequest: Content-Type

### Describe the bug

I have ran into an issue with 1.9.220 of the aws-sdk-cpp when using the WriteGetObjectResponseRequest and attempting to configure the Content-Type. When setting it . When reviewing the issues, I had found: WriteGetObjectResponseRequest: Content-Type #1665, but the ticket was already closed. I would like reopen it.

### Expected Behavior

I'd like to set the content-type to be something other than just "text/plain"

### Current Behavior

The content-type is always text/plain

### Reproduction Steps
```cpp
S3::Model::WriteGetObjectResponseRequest request;
request.WithRequestRoute(route);
request.WithRequestToken(token);
request.SetBody(objectStream);
request.SetContentType("application/json"); // <-- curl -v show "text/plain" instead
auto outcome = client.WriteGetObjectResponse(request);
```

### Possible Solution

N/A

### Additional Information/Context

_No response_

### AWS CPP SDK version used

1.9.220

### Compiler and Version used

9.4.0

### Operating System and version

Ubuntu Linux 20.04