Fix quaternion typos.

PiperOrigin-RevId: 453203844
Change-Id: I7d788c21bb00b7746f941fb2cf755f0b046e35f2

src/engine/engine_util_spatial.c

@@ -165,7 +165,7 @@ void mju_quat2Mat(mjtNum res[9], const mjtNum quat[4]) {
 
 
 
-// convert 3D rotation matrix to quaterion
+// convert 3D rotation matrix to quaternion
 void mju_mat2Quat(mjtNum quat[4], const mjtNum mat[9]) {
   // q0 largest
   if (mat[0]+mat[4]+mat[8]>0) {
@@ -214,7 +214,7 @@ void mju_derivQuat(mjtNum res[4], const mjtNum quat[4], const mjtNum vel[3]) {
 
 
 
-// integrate quaterion given 3D angular velocity
+// integrate quaternion given 3D angular velocity
 void mju_quatIntegrate(mjtNum quat[4], const mjtNum vel[3], mjtNum scale) {
   mjtNum angle, tmp[4], qrot[4];
 
@@ -257,7 +257,7 @@ void mju_quatZ2Vec(mjtNum quat[4], const mjtNum vec[3]) {
     return;
   }
 
-  // make quaterion from angle and axis
+  // make quaternion from angle and axis
   a = mju_atan2(a, mju_dot3(vn, z));
   mju_axisAngle2Quat(quat, axis, a);
 }