Modops.add_retroknowledge: remove unused argument.
Modops.add_retroknowledge: remove unused argument.

Unused since fe1979bf47951352ce32a6709cb5138fd26f311d.
I'm not sure if it was actually used back then since I didn't look at
the function it was passed to.

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