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,

src/data/coarena.rs

@@ -78,7 +78,7 @@ impl<T> Coarena<T> {
         self.data[i1 as usize] = (g1, value);
     }
 
-    /// Ensure that the given element exists in thihs coarena, and return its mutable reference.
+    /// Ensure that the given element exists in this coarena, and return its mutable reference.
     pub fn ensure_element_exist(&mut self, a: Index, default: T) -> &mut T
     where
         T: Clone,
@@ -99,7 +99,7 @@ impl<T> Coarena<T> {
         &mut data.1
     }
 
-    /// Ensure that elements at the two given indices exist in this coarena, and return their reference.
+    /// Ensure that elements at the two given indices exist in this coarena, and return their references.
     ///
     /// Missing elements are created automatically and initialized with the `default` value.
     pub fn ensure_pair_exists(&mut self, a: Index, b: Index, default: T) -> (&mut T, &mut T)

src/dynamics/joint/multibody_joint/multibody_joint_set.rs

@@ -374,7 +374,7 @@ impl MultibodyJointSet {
         ))
     }
 
-    /// Returns the the joint between two rigid-bodies (if it exists).
+    /// Returns the joint between two rigid-bodies (if it exists).
     pub fn joint_between(
         &self,
         rb1: RigidBodyHandle,