Remove --legacy-network-protocol CLI flag (#6411)

substrate/client/network/src/config.rs

@@ -425,9 +425,6 @@ pub struct NetworkConfiguration {
 	pub max_parallel_downloads: u32,
 	/// Should we insert non-global addresses into the DHT?
 	pub allow_non_globals_in_dht: bool,
-	/// If true, uses the `/<chainid>/block-requests/<version>` experimental protocol rather than
-	/// the legacy substream. This option is meant to be hard-wired to `true` in the future.
-	pub use_new_block_requests_protocol: bool,
 }
 
 impl NetworkConfiguration {
@@ -459,7 +456,6 @@ impl NetworkConfiguration {
 			},
 			max_parallel_downloads: 5,
 			allow_non_globals_in_dht: false,
-			use_new_block_requests_protocol: true,
 		}
 	}
 }