Clean up add notebook duplication in readme

[dangunter]

Developer README cleanup

Fixes #120

• Also fixed a minor issue with the default xdist (for parallel execution) 'worker', setting that to be the master (gw0) let the tests run in my environment.

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📚 Documentation preview 📚: https://idaes-examples--130.org.readthedocs.build/en/130/

[lbianchi-lbl]

I've added a CI step to run pytest . to verify that this indeed resolves #112, and reverted (and subsequently re-reverted) 9f2d61b to check that the newly added step would cause the job to fail without that change (done in 8f62fcb). So, as far as #112 is concerned, this is good to go!

[lbianchi-lbl]

From what I can see, I think this addresses the main issue of duplicated text in the developer README.