docs: remove link to edX.org-internal coursegraph queries (#28918)
docs: remove link to edX.org-internal coursegraph queries (#28918)

I had thought this wiki page was publicly accessible, but it
turns out that it is restricted to edX employees. Making the
page publicly visible would involve editing some queries
to remove edX.org-specific information, which is doable but
not something I can commit to right now.
angelapper/edx-platform,eduNEXT/edx-platform,eduNEXT/edx-platform,angelapper/edx-platform,angelapper/edx-platform,edx/edx-platform,arbrandes/edx-platform,arbrandes/edx-platform,eduNEXT/edx-platform,edx/edx-platform,angelapper/edx-platform,arbrandes/edx-platform,edx/edx-platform,arbrandes/edx-platform,eduNEXT/edx-platform,edx/edx-platform