Edge case where HRMP open request doesn't refund the deposits.

In case there is an HRMP open channel request and it is confirmed by both parties but one of the parties offboards until the end of the session, the deposit by the sender and the receiver won't be refunded.

https://github.com/paritytech/polkadot/blob/4b2bd54add5b2b4322d8479b4582f2c7290a9670/runtime/parachains/src/hrmp.rs#L651-L678

There was a discussion that it is alright to withhold the deposit of the offboarding party. This is because there is no way to ensure that because HRMP module is notified about the removal post factum so it is up to the para to claim its deposits before it offboards.