MD5加密過時方法替換

使用System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile進行MD5加密時，會出現已過時

 /// <summary>
 /// 32位MD5加密
 /// </summary>
 /// <param name="input"></param>
 /// <returns></returns>
 private static string Md5Hash(string input)
 {
     MD5CryptoServiceProvider md5Hasher = new MD5CryptoServiceProvider();
     byte[] data = md5Hasher.ComputeHash(Encoding.Default.GetBytes(input));
     StringBuilder sBuilder = new StringBuilder();
     for (int i = 0; i < data.Length; i++)
     {
         sBuilder.Append(data[i].ToString("x2"));
     }
     return sBuilder.ToString();
 }