[http-server-csharp] extra blank lines are generated in the result

For instance in this generated code:
```csharp
[ApiController]
public abstract partial class SayHiControllerBase : ControllerBase
{

internal abstract ISayHi SayHiImpl { get; }

///
/// say hello
///
[HttpPost]
[Route("/sayHi/hello")]
[ProducesResponseType((int)HttpStatusCode.OK, Type = typeof(HelloContent))]
public virtual async Task Hello(HelloContent body)
{
var result = await SayHiImpl.HelloAsync(body);
return Ok(result);
}

[HttpPost]
[Route("/sayHi/world")]
[ProducesResponseType((int)HttpStatusCode.OK, Type = typeof(WorldResult))]
public virtual async Task World()
{
var result = await SayHiImpl.WorldAsync();
return Ok(result);
}

}
}
```
There are quite a few extra blank lines which produces warnings in the project.