DOC: Documentation for the expect utility uses "expectation" instead of "reference" in embedding_distance args

[mobiware]

Issue with current documentation:

Documentation for the expect utility uses the wrong argument to the embedding_distance() method in the code sample https://docs.smith.langchain.com/how_to_guides/evaluation/unit_testing#expectations

The code sample uses the expectation arg but the real argument name is reference

Idea or request for content:

No response

[hinthornw]

Good catch