message: Minor: update plane comments
diff: @@ -127,7 +127,6 @@ public:
  /*!
  * \brief Returns a const pointer to the plane's unit normal.
  * \return N the unit normal.
  - * \post N != nullptr
  */
  AXOM_HOST_DEVICE const VectorType& getNormal() const { return m_normal; }
  @@ -196,7 +195,6 @@ private:
  *
  * \param [in] normal pointer to a buffer consisting of the normal
  * \note The supplied buffer must be at least NDIMS long.
  - * \pre normal != nullptr
  */
  AXOM_HOST_DEVICE inline void setNormal(const VectorType& normal);
  