Fix link of old astropy ideas
Fix link of old astropy ideas

OpenAstronomy/openastronomy.github.io,Cadair/openastronomy.github.io,dpshelio/openastronomy.github.io,OpenAstronomy/openastronomy.github.io,OpenAstronomy/openastronomy.github.io,Cadair/openastronomy.github.io,Cadair/openastronomy.github.io,dpshelio/openastronomy.github.io,dpshelio/openastronomy.github.io