fix: fix async_stream version (#544)

Signed-off-by: Esteve Fernandez <esteve@apache.org>

Author: esteve

rclrs/Cargo.toml

@@ -18,7 +18,7 @@ path = "src/lib.rs"
 ament_rs = { version = "0.2", optional = true }
 
 # Needed to create the GoalClientStream
-async-stream = "*"
+async-stream = "0.3.6"
 
 # Needed for uploading documentation to docs.rs
 cfg-if = "1.0.0"