fix: compile on older compilers

sdgb-cli/src/main.rs

@@ -220,7 +220,12 @@ async fn main() -> Result<(), Box<dyn snafu::Error>> {
                 .truncate(true)
                 .write(true)
                 .open("players.json")?;
-            file.lock()?;
+
+            #[rustversion::since(1.89)]
+            {
+                file.lock()?;
+            }
+
             let writer = BufWriter::new(file);
             serde_json::to_writer(writer, &user_ids)?;
             info!("dumped {} user id", user_ids.len());