doc: simplify and clarify ReferenceError material in errors.md

"should always be considered" -> "indicate"

PR-URL: #34151
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Anto Aravinth <[email protected]>
Reviewed-By: Christian Clauss <[email protected]>
Reviewed-By: Gerhard Stöbich <[email protected]>
Reviewed-By: Chengzhong Wu <[email protected]>
Reviewed-By: Andrey Pechkurov <[email protected]>

doc/api/errors.md

@@ -391,8 +391,7 @@ doesNotExist;
 ```
 
 Unless an application is dynamically generating and running code,
-`ReferenceError` instances should always be considered a bug in the code
-or its dependencies.
+`ReferenceError` instances indicate a bug in the code or its dependencies.
 
 ## Class: `SyntaxError`