removed duplicate lib.rs (#3368)

Messages are `messages` sent across chains - Messages are sent across
chains

Signed-off-by: gooddayniceday <155267459+gooddayniceday@users.noreply.github.com>

linera-sdk/src/lib.rs

@@ -117,7 +117,7 @@ pub trait Contract: WithContractAbi + ContractAbi + Sized {
 
     /// Applies a message originating from a cross-chain message.
     ///
-    /// Messages are messages sent across chains. These messages are created and received by
+    /// Messages are sent across chains. These messages are created and received by
     /// the same application. Messages can be either single-sender and single-receiver, or
     /// single-sender and multiple-receivers. The former allows sending cross-chain messages to the
     /// application on some other specific chain, while the latter uses broadcast channels to