Fix clippy warnings

Signed-off-by: Dimitris Apostolou <dimitris.apostolou@icloud.com>

crates/enostr/src/relay/message.rs

@@ -9,9 +9,7 @@ pub struct CommandResult<'a> {
 }
 
 pub fn calculate_command_result_size(result: &CommandResult) -> usize {
-    std::mem::size_of_val(result)
-        + result.event_id.as_bytes().len()
-        + result.message.as_bytes().len()
+    std::mem::size_of_val(result) + result.event_id.len() + result.message.len()
 }
 
 #[derive(Debug, Eq, PartialEq)]