Add Accept header to batch requests (Azure#24162)

Author: christothes

sdk/tables/Azure.Data.Tables/src/TableRestClient.cs

@@ -38,6 +38,7 @@ internal HttpMessage CreateBatchRequest(MultipartContent content, string request
             {
                 request.Headers.Add("Prefer", responsePreference.Value.ToString());
             }
+            request.Headers.Add("Accept", "application/json");
 
             request.Content = content;
             content.ApplyToRequest(request);