FIX: typo

src/core/js/ext_revisions.js

@@ -31,7 +31,7 @@
  * proxy (or wrapper) function adds further functionality.
  *
  * The extended update function creates a back-up version of the updated entity
- * and and adds a revisionOf property to the updated entity which references
+ * and adds a revisionOf property to the updated entity which references
  * the back-up. The back-up entity loses all of its original parents and gets
  * an "Obsolete" as only parent instead.
  *