docs: fix typo in notebook markdown block

[tenevdev]

Description

Spotted a typo while reading through the notebooks for the new course.

Affected Dependencies

n/a

How has this been tested?

n/a

Checklist

• [x] I have followed the Contribution Guidelines and Code of Conduct
• [ ] I have commented my code following the OpenMined Styleguide
• [ ] I have labeled this PR with the relevant Type labels
• [ ] My changes are covered by tests

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[IshanMi]

@yemikifouly please merge this when you get the time