[Docs] The evaluator instructions assume the menuQA flow

[mjchristy]

Describe the bug
We should update the evaluators cli commands to reference the new menuSuggestionFlow.

genkit eval:flow menuQA --input testQuestions.json

should be

genkit eval:flow menuSuggestionFlow --input testQuestions.json

And we may want to rename testQuestions to be testInputs

Docs URL
https://firebase.google.com/docs/genkit/evaluation