Kiosk Documentation: Change 10 minutes to 30 minutes

[srietkerk]

In the "add your game to kiosk" section of the kiosk docs, it says that the kiosk code only lasts 10 minutes, but it now lasts 30 minutes by default.

Here is the docs page: https://arcade.makecode.com/hardware/kiosk

[eanders-ms]

Fixed by #6192