teaching languages: fix copying of `test~object' binding to REPL

As Mike noticed, commit d836cba7c9 triggered a different binding
of `test~object' due to the enclosing module context of the `eval'ed
syntax object.

collects/lang/run-teaching-program.rkt

@@ -64,7 +64,7 @@
                                   ;; over to the one that is used in the REPL when module->namepsace
                                   ;; grabs a hold of this module to make a namespace for the REPL
                                   `(,(syntax-property
-                                      #'(define test~object (namespace-variable-value 'test~object))
+                                      #`(define #,(datum->syntax #f 'test~object) (namespace-variable-value 'test~object))
                                       'test-call #t)))
                               '())
                         ,@body-exps)))))]