[consensus] removing the `terminate` in chained_bft_smr loop
[consensus] removing the `terminate` in chained_bft_smr loop

The consensus loop/select has a terminate that should not be reachable as the loop should run forever.
This commit removes it.

Closes: #1675
Approved by: zekun000

aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,libra/libra,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core