Update py_intro.markdown

doc/py_tutorials/py_setup/py_intro/py_intro.markdown

@@ -79,8 +79,8 @@ Below is the list of contributors who submitted tutorials to OpenCV-Python.
 Additional Resources
 --------------------
 
--#  A Quick guide to Python - [A Byte of Python](http://swaroopch.com/notes/python/)
-2.  [NumPy Quickstart tutorial](https://numpy.org/devdocs/user/quickstart.html)
-3.  [NumPy Reference](https://numpy.org/devdocs/reference/index.html#reference)
-4.  [OpenCV Documentation](http://docs.opencv.org/)
+1.  [A Quick guide to Python](https://www.freecodecamp.org/news/the-python-guide-for-beginners/)
+2.  [NumPy Quickstart tutorial](https://numpy.org/doc/stable/user/quickstart.html)
+3.  [NumPy Reference](https://numpy.org/doc/stable/reference/index.html)
+4.  [OpenCV Documentation](https://docs.opencv.org/4.x/index.html)
 5.  [OpenCV Forum](https://forum.opencv.org/)