client/network: Remove option to disable yamux flow control (#7358)

With the `OnRead` flow control option yamux "send[s] window updates only
when data is read on the receiving end" and not as soon as "a Stream's
receive window drops to 0".

Yamux flow control has proven itself. This commit removes the feature
flag. Yamux flow control is now always enabled.

substrate/client/network/src/config.rs

@@ -451,7 +451,6 @@ impl NetworkConfiguration {
 				enable_mdns: false,
 				allow_private_ipv4: true,
 				wasm_external_transport: None,
-				use_yamux_flow_control: false,
 			},
 			max_parallel_downloads: 5,
 			allow_non_globals_in_dht: false,
@@ -519,8 +518,6 @@ pub enum TransportConfig {
 		/// This parameter exists whatever the target platform is, but it is expected to be set to
 		/// `Some` only when compiling for WASM.
 		wasm_external_transport: Option<wasm_ext::ExtTransport>,
-		/// Use flow control for yamux streams if set to true.
-		use_yamux_flow_control: bool,
 	},
 
 	/// Only allow connections within the same process.