Outdated Roadmap link in https://docs.boltcms.io/other/contributing#step-2-rfc-moved-to-roadmap #1287

The link in https://docs.boltcms.io/other/contributing#step-2-rfc-moved-to-roadmap links to the archived 3.x repository: https://github.com/bolt/bolt/wiki/Bolt-2.x-Roadmap. I would have submitted a PR to fix it myself, but I was not sure what the working link was (see: issue 3747 on /core).