280: Patch a Bitswap leak r=koivunej a=ljedrz We currently don't properly clean up after a connection to a `Bitswap` peer is closed, which leads to leaking `Ledger`s; funnily enough, it seems that just uncommenting a pre-existing line solves the issue. In addition, add a relevant test. Co-authored-by: ljedrz <ljedrz@gmail.com>