sc-beefy-consensus: Remove unneeded stream. (#4015)

The stream was just used to communicate from the validator the peer
reports back to the gossip engine. Internally the gossip engine just
forwards these reports to the networking engine. So, we can just do this
directly.

The reporting stream was also pumped [in the worker behind the
engine](https://github.com/paritytech/polkadot-sdk/blob/9d626189/substrate/client/consensus/beefy/src/worker.rs#L939).
This means if there was a lot of data incoming over the engine, the
reporting stream was almost never processed and thus, it could have
started to grow and we have seen issues around this.

Partly Closes: https://github.com/paritytech/polkadot-sdk/issues/3945