Revert "Update wiki.libsdl.org urls to libsdl-org/SDL/wiki (#4069)" This reverts commit 82a96afa70212da94de758df859e94cccdb2c805. We ended up not moving to GitHub's wiki after all and built https://github.com/icculus/ghwikipp to fill the gap...since the wiki is back at https://wiki.libsdl.org/, put back the original URLs.