Tutorial: Explain the difference between confidence and evaluation score

Refs https://redmine.teklia.com/issues/7670

Could you improve the tutorial with what you said in https://redmine.teklia.com/issues/6775#note-37?

• Adding Evaluation score and Confidence score to the Lexicon
• Adding a quick paragraph to explain that we do not calculate the evaluation score in the tutorial as it would require to run scoring tools out of the box in Visualizing predictions sections (or elsewhere if that is not suitable...)