nixos/doc: move implementation notes for formats.hocon to docs

(cherry picked from commit 141a8a6c86)

nixos/doc/manual/development/settings-options.section.md

@@ -199,6 +199,14 @@ have a predefined type and string generator already declared under
           }
         ```
 
+    `Implementation notes:`
+
+    - classpath includes are not implemented in pyhocon,
+      which is used for validating the HOCON output. This
+      means that if you are using classpath includes,
+      you will want to either use an alternative validator
+      or set `doCheck = false` in the format options.
+
 `pkgs.formats.json` { }
 
 :   A function taking an empty attribute set (for future extensibility)

pkgs/pkgs-lib/formats/hocon/default.nix

@@ -27,13 +27,9 @@ let
   '';
 in
 {
-  # https://github.com/lightbend/config/blob/main/HOCON.md
   format = {
     generator ? hocon-generator
     , validator ? hocon-validator
-    # `include classpath("")` is not implemented in pyhocon.
-    # In the case that you need this functionality,
-    # you will have to disable pyhocon validation.
     , doCheck ? true
   }: let
     hoconLib = {