Update exercises/exercise-coupling-ff-pm/README.md

exercises/exercise-coupling-ff-pm/README.md

@@ -164,9 +164,9 @@ auto elementSelectorDarcy = [&](const auto& element)
 };
 ```
 
-Make sure, that you have uncommented the lines including the gridcreators in both problem files
+Make sure, that you have uncommented the lines including the grid managers in both problem files
 ```cpp
-#include <dumux/io/grid/subgridgridcreator.hh>
+#include <dumux/io/grid/subgridmanager.hh>
 ```
 
 and do the changes in the respective lines for the `Grid` property.