Fix JSON serialization issue with double-commas

… I forgot to add an output to YASON:ENCODE!

src/activity-vocabulary.lisp

@@ -280,7 +280,8 @@ into one. Otherwise, parse it into an associative list."
 ;;; ————————————————————————————————————————
 ;; Note-worthy: See the above-defined DEFINE-YASON-ENCODE-SLOTS.
 (defmethod yason:encode ((obj object) &optional (stream *standard-output*))
-  (yason:encode-object obj))
+  (yason:with-output (stream)
+    (yason:encode-object obj)))
 
 (defmethod yason:encode-object ((obj object))
   (typecase *@context*
@@ -301,8 +302,6 @@ into one. Otherwise, parse it into an associative list."
 their sanitized string keys appropriate for ActivityVocabular custom.
 A class with slots MAP-AWAY and COLLECTION-AGAIN would return
   ((MAP-AWAY . “mapAway”)(COLLECTION-AGAIN . “collectionAgain”))"
-;;  (alist-remove-keys
-;;   'type
   (alist-mapcdr #'camel-case
                 (class-slots-alist class)))
 
@@ -356,12 +355,6 @@ items in each will be contained in the resultant list."
   (mapcar (lambda (sym) (find-class sym))
           (find-registered-symbols str)))
 
-(defun alist-remove-keys (item alist &optional (test #'equal))
-  "Remove cells from an associative list whose key TESTs as ITEM."
-  (cl:remove item alist
-             :test (lambda (a cell)
-                     (funcall test a (car cell)))))
-
 (defun alist-mapcdr (function alist)
   "Apply a FUNCTION to all values (cdrs) of an ALIST’s pairs. Returns a new ALIST
 of the same keys, whose values are the results of FUNCTION."