lib/modules: hide _module.args docs

unfortunately we can't unconditionally make this text markdown without
impacting downstream users of docs generation (as noted in #175586).
hide it entirely until the transition is complete.

lib/modules.nix

@@ -157,6 +157,11 @@ rec {
             ${if prefix == []
               then null  # unset => visible
               else "internal"} = true;
+            # TODO: hidden during the markdown transition to not expose downstream
+            # users of the docs infra to markdown if they're not ready for it.
+            # we don't make this visible conditionally because it can impact
+            # performance (https://github.com/NixOS/nixpkgs/pull/208407#issuecomment-1368246192)
+            visible = false;
             # TODO: Change the type of this option to a submodule with a
             # freeformType, so that individual arguments can be documented
             # separately