README: Remove broken link to Dev Center article (#1171)
README: Remove broken link to Dev Center article (#1171)

The article no longer exists (the solution it recommended was out of date),
and the README also isn't really the best place for this kind of content.

Closes GUS-W-8884544.

[skip changelog]
heroku/heroku-buildpack-python,heroku/heroku-buildpack-python,Scalingo/python-buildpack,AltSchool/heroku-buildpack-python,Scalingo/python-buildpack,AltSchool/heroku-buildpack-python