[exercises][dunemodule] Update statements corresponding to opts files.

exercises/exercise-dunemodule/README.md

@@ -31,7 +31,7 @@ The following command will configure your new module
 ./dune-common/bin/dunecontrol --opts=<opts file> --only=dumux-example all
 ```
 
-You need to run this command in the folder with content dumux, dumux-course, dune-common, dune-geometry, dune-grid, dune-istl, etc. `<opts file>` needs to be replaced (please replace the angle brackets also) by an options file, e.g. by `./dumux/optim.opts` or `./dumux/debug.opts`. optim.opts is faster - debug.opts allows for debugging.
+You need to run this command in the folder with content dumux, dumux-course, dune-common, dune-geometry, dune-grid, dune-istl, etc. `<opts file>` needs to be replaced (please replace the angle brackets also) by an options file, e.g. by `./dumux/cmake.opts`. Have a look at the comments in this file to see how you can adapt it to your needs.
 
 <hr><br><br>
 ### Task 3: Create a new test case within your new DuMuX module