Fix typos in docs and param yamls

[MImmesberger]

What problem do you want to solve?

• The yaml dump/load example was slightly wrong in simple_examples.ipynb (discovered by @felixschmitz)
• The lookup table for the threshold age of one phased-out pathway into retirement ends with birth year 1951. It should be much longer because we take care of eligibility checks elsewhere.

[read-the-docs-community]

Documentation build overview

📚 gettsim | 🛠️ Build #29433102 | 📁 Comparing f68b753 against latest (7f49854)

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Show files changed (3 files in total): 📝 3 modified | ➕ 0 added | ➖ 0 deleted

File	Status
how_to_guides/modifications_of_policy_environments.html	📝 modified
tutorials/simple_example.html	📝 modified
tutorials/visualizing_the_system.html	📝 modified

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[MImmesberger]

We can merge or leave open in case something else comes up in the next few days (quite likely I'd say) @hmgaudecker

[hmgaudecker]

Thanks!

We can merge or leave open in case something else comes up in the next few days (quite likely I'd say) @hmgaudecker

As you prefer!