update comments and reorganize a bit the .gitlab-ci.yml
update comments and reorganize a bit the .gitlab-ci.yml

Comments about artifacts and needs were outdated (seems to be from
when we still had stages, for instance not-a-real-job was really
needed back then as with stages no needs meant needs: all previous stages)

Zimmi48/coq,ejgallego/coq,coq/coq,SkySkimmer/coq,Zimmi48/coq,coq/coq,ejgallego/coq,ejgallego/coq,SkySkimmer/coq,SkySkimmer/coq,ejgallego/coq,coq/coq,Zimmi48/coq,SkySkimmer/coq,Zimmi48/coq,coq/coq