[Cleanup] Fix up labelling: Swap rear/front

src/sand-wedge-data/mygrid.cc

@@ -208,11 +208,11 @@ MyFaces<GridView>::MyFaces(GridView const &gridView)
   });
 #if DIM == 3
   front.insertFacesByProperty([&](typename GridView::Intersection const &in) {
-    return isClose(-MyGeometry::depth / 2.0, in.geometry().center()[2]);
+    return isClose(MyGeometry::depth / 2.0, in.geometry().center()[2]);
   });
 
   back.insertFacesByProperty([&](typename GridView::Intersection const &in) {
-    return isClose(MyGeometry::depth / 2.0, in.geometry().center()[2]);
+    return isClose(-MyGeometry::depth / 2.0, in.geometry().center()[2]);
   });
 #endif