Use table prefix when deleting from region_poly2d_point.

src/main/java/com/sk89q/worldguard/protection/databases/MySQLDatabase.java

@@ -1029,7 +1029,7 @@ private void updatePoly2dPoints(ProtectedPolygonalRegion region) throws SQLExcep
 
         try {
             clearPoly2dPointsForRegionStatement = this.conn.prepareStatement(
-                    "DELETE FROM `region_poly2d_point` " +
+                    "DELETE FROM `" + config.sqlTablePrefix + "region_poly2d_point` " +
                     "WHERE `region_id` = ? " +
                     "AND `world_id` = " + this.worldDbId
             );