Clean up mirror-dispatcher.js
While looking into #15750, I saw there was some old code which is now obsolete. It was used by DAVE, but since we switched to VE, it’s not necessary.
This is not urgent and can be reviewsd at any time - maybe when we release the next version of the verification extension, so it can be tested at the same time.
Feature Branch: mirror-pool-dispatcher.git:feature/15750+cleanup