Dispose stream in caller method

Author: MaggieKimani1

src/Microsoft.OpenApi/Reader/OpenApiModelFactory.cs

@@ -128,6 +128,7 @@ public static async Task<ReadResult> LoadAsync(Stream input, string format = nul
             if (!settings.LeaveStreamOpen)
             {
                 input.Dispose();
+                preparedStream.Dispose();
             }
 
             return result;