fixed VehicleBase syntax error: ._accelMax -> _accel_max (typo) (#422)

Author: JoachimDunkel

roboticstoolbox/mobile/Vehicle.py

@@ -400,7 +400,7 @@ def limits_va(self, v, v_prev):
         vp = v_prev[0]
         if self._accel_max is not None:
             if (v - vp) / self._dt > self._accel_max:
-                v = vp + self._accelmax * self._dt
+                v = vp + self._accel_max * self._dt
             elif (v - vp) / self._dt < -self._accel_max:
                 v = vp - self._accel_max * self._dt
         v_prev[0] = v