Remove evidence sending in the audit announcement

[alxmirap]

In CE 144, we currently send an announcement and associated evidence for the other validators to check the announcement is legitimate.
This does not seem to be required by Elves, and so the whole evidence part could be removed.

[burdges]

There are many incorrect statements around ELVES in the JAM paper. In this case, there was seemingly an assumption that we'd have concensus upon approval checkers. ELVES does not require concensus upon who does which approval checks, merely that everyone would check eventually, the back pressure to make this safe, and that usually enough protocol messages arrive so that everything runs fast. We've have a messy censorship problem if we did obtain concensus upon cehckers anyways.

Rewards should handled by some service, not the RC itself, ala polkadot-fellows/RFCs#119 In fact, backers/garantors should not be paid by the RC either, because their rewards must not be "better" than the approval checkers rewards, in particular backer rewawards should not be more relaible than approval cehcker rewards.