Add missing sip binding

(cherry-picked from 37ef6b8)

Author: nyalldawson

python/core/qgspallabeling.sip

@@ -103,6 +103,7 @@ class QgsPalLayerSettings
       Horizontal, /**< Arranges horizontal candidates scattered throughout a polygon feature. Applies to polygon layers only.*/
       Free, /**< Arranges candidates scattered throughout a polygon feature. Candidates are rotated to respect the polygon's orientation. Applies to polygon layers only.*/
       OrderedPositionsAroundPoint, /**< Candidates are placed in predefined positions around a point. Peference is given to positions with greatest cartographic appeal, eg top right, bottom right, etc. Applies to point layers only.*/
+      PerimeterCurved, /** Arranges candidates following the curvature of a polygon's boundary. Applies to polygon layers only.*/
     };
 
     //! Positions for labels when using the QgsPalLabeling::OrderedPositionsAroundPoint placement mode