bad templates in histc

Former-commit-id: 23c58060dc3d2ead7699c464676910bebbc92dd6

include/igl/histc.cpp

@@ -78,7 +78,7 @@ IGL_INLINE void igl::histc(
   }
 }
 
-template <typename DerivedX, typename DerivedE, typename DerivedB>
+template <typename DerivedE>
 IGL_INLINE void igl::histc(
     const typename DerivedE::Scalar & x,
     const Eigen::PlainObjectBase<DerivedE > & E,