Remove "boundary" on content-type for /identification

This is not a multipart request, and thus should not have boundary
name set in the content-type header. This is an old 2015 copy paste-bug

Author: eivinhb

Digipost.Api.Client.Send/Actions/IdentificationAction.cs

@@ -20,9 +20,7 @@ internal override HttpContent Content(IIdentification requestContent)
             var xmlMessage = Serialize(requestContent);
             var messageContent = new StringContent(xmlMessage);
 
-            var boundary = Guid.NewGuid().ToString();
             var mediaTypeHeaderValue = new MediaTypeHeaderValue(DigipostVersion.V8);
-            mediaTypeHeaderValue.Parameters.Add(new NameValueWithParametersHeaderValue("boundary", boundary));
             messageContent.Headers.ContentType = mediaTypeHeaderValue;
 
             return messageContent;