test-ob-exp: fix failing test

* testing/lisp/test-ob-exp.el (ob-exp/export-from-a-temp-buffer):
  Check for the correct expected output so the test stops failing.

testing/lisp/test-ob-exp.el

@@ -259,7 +259,6 @@ Here is one at the end of a line. =2=
 			    result)))))
 
 (ert-deftest ob-exp/export-from-a-temp-buffer ()
-  :expected-result :failed
   (org-test-with-temp-text
       "
 #+Title: exporting from a temporary buffer
@@ -279,8 +278,9 @@ Here is one at the end of a line. =2=
 #+END_SRC
 "
     (let* ((ascii (org-export-as 'ascii)))
-      (should (string-match (regexp-quote (format nil "%S" '(:foo :bar)))
-			    ascii)))))
+      (should (string-match
+	       (regexp-quote " :foo  :bar \n")
+			     ascii)))))
 
 (ert-deftest ob-export/export-with-results-before-block ()
   "Test export when results are inserted before source block."