rpc: add rpc v2 chainSpec to polkadot (#2859)

The [chainSpec RPC API from the v2
spec](https://paritytech.github.io/json-rpc-interface-spec/api/chainSpec.html)
was only added to substrate-node and should be added to polkadot as well

/cc @lexnv

substrate/client/consensus/beefy/src/import.rs

@@ -148,7 +148,7 @@ where
 				// The block is imported as part of some chain sync.
 				// The voter doesn't need to process it now.
 				// It will be detected and processed as part of the voter state init.
-				return Ok(inner_import_result);
+				return Ok(inner_import_result)
 			},
 		}