Remove ?@fun error msg

Author: YingboMa

src/types.jl

@@ -200,8 +200,7 @@ struct FnType{X<:Tuple,Y} end
 
 function (f::Symbolic)(args...)
     error("Sym $f is not callable. " *
-          "Use @syms $f(var1, var2,...) to create it as a callable. " *
-          "See ?@fun for more options")
+          "Use @syms $f(var1, var2,...) to create it as a callable.")
 end
 
 """