Fix #10413 (CI failure on tags).
Fix #10413 (CI failure on tags).

On tags, the pkg:nix:deploy:channel job was run even though the
required pkg:nix:deploy was not.  We repeat the same conditions
regarding refs as in pkg:nix:deploy.  Cf. GitLab's doc on the meaning
of several only conditions:
https://docs.gitlab.com/ee/ci/yaml/README.html#onlyexcept-advanced

JasonGross/coq,ejgallego/coq,ejgallego/coq,ejgallego/coq,JasonGross/coq,JasonGross/coq,SkySkimmer/coq,coq/coq,SkySkimmer/coq,Matafou/coq,coq/coq,Zimmi48/coq,Zimmi48/coq,gares/coq,gares/coq,Matafou/coq,silene/coq,SkySkimmer/coq,gares/coq,Matafou/coq,SkySkimmer/coq,ejgallego/coq,coq/coq,JasonGross/coq,Zimmi48/coq,Zimmi48/coq,gares/coq,silene/coq,coq/coq,silene/coq,gares/coq