Update notebook because of changes in block triangularization

[dallan-keylogic]

Fix notebook for new block triangularization

The PR IDAES/idaes-pse#1704 changes how the BlockTriangularizationInitializer works, which results in a unit model in the custom unit model notebook raising an exception. This exception is the result of problems in the unit model that are then diagnosed with the Diagnostics Toolbox. In order to avoid test failures, we wrap the initialization in a try/except block.

---

Legal Acknowledgement

By contributing to this software project, I agree to the following terms and conditions for my contribution:

I agree my contributions are submitted under the license terms described in the LICENSE.txt file at the top level of this directory.
I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

---

📚 Documentation preview 📚: https://idaes-examples--157.org.readthedocs.build/en/157/

[bpaul4]

Downloaded and compared changes with version on main. I agree with the changes.