Trivial comment typos corrected.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>

koha-tmpl/intranet-tmpl/prog/en/modules/cataloguing/additem.tmpl

@@ -120,14 +120,14 @@ function CloneSubfield(index){
         }
     }
     catch(e){
-        // do nothig if ButtonPlus & CloneButtonPlus don't exist.
+        // do nothing if ButtonPlus & CloneButtonPlus don't exist.
     }
     // insert this line on the page
     original.parentNode.insertBefore(clone,original.nextSibling);
 }
 
 /**
- * This function create a random number
+ * This function creates a random number
  */
 function CreateKey(){
     return parseInt(Math.random() * 100000);