[IMPR] Reduce deprecated stuff in requests-requirements.txt
[IMPR] Reduce deprecated stuff in requests-requirements.txt

The file still needs to be updated on every change of requests dependency. This
patch will move the dependency to setup.py.

The dot installs pywikibot, requests, requests dependencies and requests
security per the specification in setup.py.

Detached from I9cf5fa2acaf65

Bug: T193476
Change-Id: I6618d680fd5d2ce57b1a8c9ee79abf7ab59d20ab

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