[GAMEPLAY] Upgrading Forbidden Idol into Redemtion gives bonus cdr. for a short duration

Found this while using the practice tool. When I upgraded Forbidden Idol into Redemption I got 10% bonus cdr, on top of the 10% Redemption gives. Seems like the cdr of the two items stack. However, it only lasted for 5-10 seconds. The cooldown of my q went down, so it wasn't only a bug in the hud

Things I did that might have had an effect:

• Played in practice tool
• Played Soraka
• Used the thing that gives a lot of gold - Bought and sold several cdr-granting items in a row (checked myself: didn't have an effect)