remove leftover, dublicate conversion

src/conversions.jl

@@ -302,7 +302,7 @@ end
 
 
 ################################################################################
-#                                 SurfaceLike                                  #
+#                                  GridBased                                   #
 ################################################################################
 
 function edges(v::AbstractVector)
@@ -636,21 +636,6 @@ function convert_arguments(::VolumeLike, x::AbstractVector, y::AbstractVector, z
     return (x, y, z, el32convert.(f.(_x, _y, _z)))
 end
 
-"""
-    convert_arguments(P, x, y, f)::(Vector, Vector, Matrix)
-
-Takes vectors `x` and `y` and the function `f`, and applies `f` on the grid that `x` and `y` span.
-This is equivalent to `f.(x, y')`.
-`P` is the plot Type (it is optional).
-"""
-function convert_arguments(sl::SurfaceLike, x::AbstractVector{T1}, y::AbstractVector{T2},
-                           f::Function) where {T1,T2}
-    if !applicable(f, x[1], y[1])
-        error("You need to pass a function with signature f(x::$T1, y::$T2). Found: $f")
-    end
-    return convert_arguments(sl, x, y, f.(x, y'))
-end
-
 function convert_arguments(P::PlotFunc, r::AbstractVector, f::Function)
     return convert_arguments(P, r, map(f, r))
 end