Update Chp_02.ipynb

[rvcoile]

correction so the posterior integrates to unity

Thank you for opening a pull request!

Please check our style guide, and also make sure that the notebooks you've modified pass the pre-commit checks. If, for example, you modified notebook1.ipynb and notebook2.ipynb, you could do this by running:

pre-commit run --files notebook1.ipynb notebook2.ipynb

You may need to run it a couple of times before all the checks pass.

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB

[olszewskip]

An analogous change could/should be made in solutions 2M[1-2] to this chapter.

[canyon289]

hi @rvcoile, can you run precommit pre-commit run --all-files to update these files? It'll get the notebook up the same standard as the rest automagically

https://github.com/pymc-devs/resources/runs/5618658061?check_suite_focus=true#step:4:83