doc: clarify util.inspect usage intent

PR-URL: nodejs#17375
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Benjamin Gruenbaum <[email protected]>
Reviewed-By: Sakthipriyan Vairamani <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>

Author: devsnek

doc/api/util.md

@@ -348,8 +348,9 @@ changes:
     line. Defaults to 60 for legacy compatibility.
 
 The `util.inspect()` method returns a string representation of `object` that is
-primarily useful for debugging. Additional `options` may be passed that alter
-certain aspects of the formatted string.
+intended for debugging. The output of `util.inspect` may change at any time
+and should not be depended upon programmatically. Additional `options` may be
+passed that alter certain aspects of the formatted string.
 `util.inspect()` will use the constructor's name and/or `@@toStringTag` to make an
 identifiable tag for an inspected value.