[ci] Disable the OCaml 4.12 target
[ci] Disable the OCaml 4.12 target

Recent changes in Coqbot plus the unfortunate breakage OCaml upstream
has make this too noisy.

We will re-enable once https://github.com/ocaml/dune/pull/3585
is accepted upstream.

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