fix dynamic-require with symbol to not make available

to match behavior in docs and racket 6.

pkgs/racket-test-core/tests/racket/module.rktl

@@ -2456,6 +2456,29 @@ case of module-leve bindings; it doesn't cover local bindings.
   (check '(begin-for-syntax (struct bar ())) #rx"later defined as syntax")
   (check '(require (for-syntax (only-in racket/base [car bar]))) #rx"later bound differently"))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Check that dynamic-require with a symbol argument
+;; does not make the required module available for visits
+
+(module shouldntvisit racket/base
+  (define x 5)
+  (provide x)
+  (require (for-syntax racket/base))
+  (define-for-syntax v #f)
+  (define-syntax (m stx)
+    (set! v #t)
+    #'(void))
+  (m)
+  (begin-for-syntax
+    (when (not v)
+      (error 'shouldntvisit "visited"))))
+
+(module visitor racket/base
+  (require (for-syntax racket/base))
+  (begin-for-syntax
+    (dynamic-require ''shouldntvisit 'x))
+  (begin-for-syntax))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (report-errs)

racket/src/expander/eval/dynamic-require.rkt

@@ -70,7 +70,8 @@
       (define binding (provided-as-binding binding/p))
       (define ex-sym (module-binding-sym binding))
       (define ex-phase (module-binding-phase binding))
-      (namespace-module-instantiate! ns mpi phase #:run-phase phase)
+      (namespace-module-instantiate! ns mpi phase #:run-phase phase
+                                     #:otherwise-available? #f)
       (define ex-mod-name (module-path-index-resolve
                            (module-path-index-shift
                             (module-binding-module binding)