updated syntax

tutorials/mesh/snappyHexMesh/iglooWithFridges/system/snappyHexMeshDict

@@ -45,6 +45,8 @@ geometry
     fridgeFreezer
     {
         type searchableSurfaceCollection;
+
+        mergeSubRegions true;
     
         freezer
         {
@@ -75,6 +77,8 @@ geometry
     {
         type searchableSurfaceCollection;
     
+        mergeSubRegions true;
+    
         seal
         {
             surface fridgeFreezer;