docs: markdown: fixed more external links that still point to wiki.nginx.org.
docs: markdown: fixed more external links that still point to wiki.nginx.org.

yeahdongcn/SEnginx,yeahdongcn/SEnginx,yeahdongcn/SEnginx,yeahdongcn/SEnginx,yeahdongcn/SEnginx,yeahdongcn/SEnginx,yeahdongcn/SEnginx