expander: declare readtable structure as #:authentic

racket/src/expander/read/readtable.rkt

@@ -30,7 +30,8 @@
                    ;; 'no-delimit, or a character whose default to use;
                    ;; absence of a mapping is the default for that character
                    delimiter-ht)
-  #:property prop:readtable #t)
+  #:property prop:readtable #t
+  #:authentic)
 
 (define (make-readtable rt . args)
   (unless (or (not rt) (readtable? rt))

racket/src/racket/src/startup.inc

@@ -48224,7 +48224,7 @@ static const char *startup_source =
 " 4"
 " 0"
 " #f"
-"(list(cons prop:readtable #t))"
+"(list(cons prop:authentic #t)(cons prop:readtable #t))"
 "(current-inspector)"
 " #f"
 " '(0 1 2 3)"