grid: avoid clone of buffer

src/grid.rs

@@ -139,11 +139,9 @@ impl Grid {
             ..
         } = self.config;
 
-        let buf = self.buf.clone();
-
         self.agents.par_iter_mut().for_each(|agent| {
             agent.tick(
-                &buf,
+                &self.buf,
                 sensor_distance,
                 sensor_angle,
                 rotation_angle,