fix no_std build

satrs/src/tmtc/mod.rs

@@ -7,18 +7,18 @@
 //! all received telecommands are sent to a special handler object called TC source. Using
 //! a design like this makes it simpler to add new TC packet sources or new telemetry generators:
 //! They only need to send the received and generated data to these objects.
-use std::sync::mpsc;
-
 #[cfg(feature = "alloc")]
 use downcast_rs::{impl_downcast, Downcast};
 use spacepackets::SpHeader;
+#[cfg(feature = "std")]
+use std::sync::mpsc;
+#[cfg(feature = "std")]
+use crate::queue::GenericSendError;
 
 #[cfg(feature = "std")]
 pub mod tc_helper;
 pub mod tm_helper;
 
-use crate::queue::GenericSendError;
-
 /// Generic trait for object which can receive any telecommands in form of a raw bytestream, with
 /// no assumptions about the received protocol.
 ///