Fix more typos. (#712)

These are ones not found by `typos` for various reasons.

src/counters/collision_detection_counters.rs

@@ -22,7 +22,7 @@ impl CollisionDetectionCounters {
         }
     }
 
-    /// Resets all the coounters and timers.
+    /// Resets all the counters and timers.
     pub fn reset(&mut self) {
         self.ncontact_pairs = 0;
         self.broad_phase_time.reset();

src/counters/mod.rs

@@ -23,7 +23,7 @@ pub struct Counters {
     pub step_time: Timer,
     /// Timer used for debugging.
     pub custom: Timer,
-    /// Counters of every satge of one time step.
+    /// Counters of every stage of one time step.
     pub stages: StagesCounters,
     /// Counters of the collision-detection stage.
     pub cd: CollisionDetectionCounters,