[doc] [sphinx] Be silent when running latexmk
[doc] [sphinx] Be silent when running latexmk

This is actually supported by Sphinx directly.

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