github-ci: port send-telegram-notify to python3

For now python3 is used as the default python on all OS and it is
needed to enable it in send-telegram-notify action.

Found issue:

  Traceback (most recent call last):
    File "<string>", line 3, in <module>
  AttributeError: module 'urllib' has no attribute 'quote_plus'

In Python 3 quote_plus included into urllib.parse.

Check documentaion [1]:

  Note The urllib module has been split into parts and renamed in Python 3 to urllib.request, urllib.parse, and urllib.error.

Check the same issue [2].

This patch changes use of all needed routines just from 'urllib'.

Closes tarantool/tarantool-qa#112

[1]: https://docs.python.org/2/library/urllib.html
[2]: https://github.com/web2py/web2py/issues/1822