Make relayer_session module public (#3082)

This makes `RelayerSessionTask` usable directly as Rust a crate dependency.

apps/pyth-lazer-agent/src/main.rs

@@ -12,7 +12,7 @@ mod http_server;
 mod jrpc_handle;
 mod lazer_publisher;
 mod publisher_handle;
-mod relayer_session;
+pub mod relayer_session;
 mod websocket_utils;
 
 #[derive(Parser, Deserialize)]