fixup! repl: move completion logic to internal module

add comment to `getReplBuiltinLibs` and `setReplyBuiltinLibs` functions

Author: dario-piotrowicz

lib/internal/repl/utils.js

@@ -823,6 +823,12 @@ let _builtinLibs = ArrayPrototypeFilter(
   (e) => e[0] !== '_' && !StringPrototypeStartsWith(e, 'node:'),
 );
 
+// Note: the `getReplBuiltinLibs` and `setReplBuiltinLibs` are functions used to provide getters and
+//       setters for the `builtinModules` and `_builtinLibs` properties of the repl module and for making
+//       sure that all internal repl modules share the same value, which can potentially be updated by users.
+//       Also note that both `repl.builtinModules` and `repl._builtinLibs` are deprecated, once such properties
+//       are removed these two functions should also be removed as no longer necessary.
+
 function getReplBuiltinLibs() {
   return _builtinLibs;
 }