Drop incorrect and obsolete Rustler.nif_versions function

Author: filmor

rustler_mix/lib/rustler.ex

@@ -171,14 +171,4 @@ defmodule Rustler do
 
   @doc false
   def rustler_version, do: "0.32.1"
-
-  @doc """
-  Supported NIF API versions.
-  """
-  def nif_versions,
-    do: [
-      ~c"2.14",
-      ~c"2.15",
-      ~c"2.16"
-    ]
 end

rustler_mix/lib/rustler/compiler/messages.ex

@@ -61,13 +61,4 @@ defmodule Rustler.Compiler.Messages do
     Note: You should already have this if you made your project with the project generator.
     """
   end
-
-  def message({:unsupported_nif_version, version}) do
-    """
-    Your current version of Erlang is on NIF version '#{version}'.
-    Rustler currently supports versions #{inspect(Rustler.nif_versions())}.
-
-    Go open an issue about this on github!
-    """
-  end
 end