[cleanup] Cleanup dependency_links in setup.py
[cleanup] Cleanup dependency_links in setup.py

- pywinauto and pywin32 are available via pypi
- dependency_links wheren't processed since pip 1.4 due to a missing
  --process-dependency-links option and is droppend since pip 19.0

Change-Id: I5580cc31204a1ee21dc79302b6aee0fbbef1bb44

wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core