LibWeb/IDB: Implement IDBCursor::update

Author: https://github.com/stelar7
Commit: cf84a98bab
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4720
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/AtkinsSJ ✅
Reviewed-by: https://github.com/shannonbooth

Libraries/LibWeb/IndexedDB/IDBCursor.idl

@@ -10,7 +10,7 @@ interface IDBCursor {
     undefined advance([EnforceRange] unsigned long count);
     undefined continue(optional any key);
     undefined continuePrimaryKey(any key, any primaryKey);
-    [FIXME, NewObject] IDBRequest update(any value);
+    [NewObject] IDBRequest update(any value);
     [FIXME, NewObject] IDBRequest delete();
 };