Fix docs for Tet14::default_order()

Author: nmnobre

include/geom/cell_tet14.h

@@ -147,7 +147,7 @@ class Tet14 final : public Tet
   virtual bool has_affine_map () const override;
 
   /**
-   * \returns SECOND.
+   * \returns THIRD.
    */
   virtual Order default_order() const override;