[Docs] Remove mention of Bountysource
[Docs] Remove mention of Bountysource

It failed to gain any traction.

tejasbubane/rubocop,jmks/rubocop,bbatsov/rubocop,bbatsov/rubocop,tdeo/rubocop,jmks/rubocop,maxjacobson/rubocop,maxjacobson/rubocop,tejasbubane/rubocop,rrosenblum/rubocop,maxjacobson/rubocop,tejasbubane/rubocop,jmks/rubocop,tdeo/rubocop,tdeo/rubocop,rrosenblum/rubocop,rrosenblum/rubocop