update wflow build notebook

[hboisgon]

Issue addressed

Fixes #256

Explanation

We removed default merit_hydro value in setup_basemaps so the example of building a model without suppliying a config file does not work anymore. The behavior is anyway not common and will be deprecated in hydromt v1 so I now removed that part of the example.

Checklist

• [x] Updated tests or added new tests
• [x] Branch is up to date with main
• [x] Tests & pre-commit hooks pass
• [x] Updated documentation if needed