text: Title: Broken documentation links on Gensim's PyPI page
  Body: Links in the `Documentation` section of our official PyPI page are broken (return 404): 
  https://pypi.org/project/gensim/#documentation-1
  
  OTOH, links at https://github.com/RaRe-Technologies/gensim#documentation work, so it looks like the PyPI version contains obsolete links that got out of sync.
  