Update tutorial.md

[nekrut]

Fixed broken image link

[github-actions]

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training-material/topics/data-science/tutorials/gnmx-lecture6/tutorial.md

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> Image from [Pandas Docs](https://pandas.pydata.org/docs/getting_started/intro_tutorials/07_reshape_table_layout.html#wide-to-long-format).

[github-actions]

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training-material/topics/data-science/tutorials/gnmx-lecture6/tutorial.md

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> Image from [Pandas Docs](https://pandas.pydata.org/docs/getting_started/intro_tutorials/07_reshape_table_layout.html#long-to-wide-table-format).

[github-actions]

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Potential broken box. A None was opened on 628, but not closed on line 629

training-material/topics/data-science/tutorials/gnmx-lecture6/tutorial.md

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> Figure from Wikimedia Commons

[github-actions]

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training-material/topics/data-science/tutorials/gnmx-lecture6/tutorial.md

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> Figure from Wikimedia Commons

[github-actions]

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training-material/topics/data-science/tutorials/gnmx-lecture6/tutorial.md

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> Figure from Wikimedia Commons

[github-actions]

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Potential broken box. A None was opened on 684, but not closed on line 685

training-material/topics/data-science/tutorials/gnmx-lecture6/tutorial.md

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> Figure from Wikimedia Commons