Fix mermaid_include_elk in conf.py for sphinx-mermaid 2.0.0

[psobolewskiPhD]

sphinxcontrib-mermaid had a new release with breaking changes, and we don't pin it. So you need to change this line

https://github.com/napari/docs/blob/1f9759bc61c0697cdbf9f805e334dbbc4b2fca28/docs/conf.py#L200C1-L200C25

to read

mermaid_include_elk = False

and the build works (tested locally)

You can see the config value here: https://sphinxcontrib-mermaid-demo.readthedocs.io/en/stable/ (old version) and here https://sphinxcontrib-mermaid-demo.readthedocs.io/en/latest/#mermaid-include-elk (new version)

Originally posted by @melissawm in #908 (comment)