ci: use fixed telnetlib since python 3.13 removed this from stdlib

conftest.py

@@ -18,7 +18,6 @@ import sys
 import time
 import xml.etree.ElementTree as ET
 from fnmatch import fnmatch
-from telnetlib import Telnet
 from typing import Any
 from typing import Callable
 from typing import List
@@ -43,6 +42,7 @@ from pytest_embedded.utils import to_bytes
 from pytest_embedded.utils import to_str
 from pytest_embedded_idf.dut import IdfDut
 from pytest_embedded_idf.unity_tester import CaseTester
+from pytest_embedded_jtag._telnetlib.telnetlib import Telnet  # python 3.13 removed telnetlib, use this instead
 
 try:
     from idf_ci_utils import to_list