Fixes in OOP notebook (#340)

* fixes in oop notebook

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* more text fixes

* final fixes

* Update tutorial/tests/test_05_object_oriented_programming.py

Co-authored-by: Edoardo Baldi <edoardo.baldi@empa.ch>

* fix links

* Update 05_object_oriented_programming.ipynb

Co-authored-by: Pascal Su <pascal.su@empa.ch>

* fix person comparison exercise

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* fix ice cream shop exercise

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update 05_object_oriented_programming.ipynb

Co-authored-by: Pascal Su <pascal.su@empa.ch>

* fixes after review

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Edoardo Baldi <edoardo.baldi@empa.ch>
Co-authored-by: Pascal Su <pascal.su@empa.ch>

Author: 4 people