Fix incorrect filename references

[robertoea]

Minor typo corrections. I changed the filenames in the example folder structure instead of the later references to be consistent with the other examples in the documentation.

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In case of fundamental code change, Airflow Improvement Proposal (AIP) is needed.
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[boring-cyborg]

Congratulations on your first Pull Request and welcome to the Apache Airflow community! If you have any issues or are unsure about any anything please check our Contribution Guide (https://github.com/apache/airflow/blob/main/CONTRIBUTING.rst)
Here are some useful points:

• Pay attention to the quality of your code (flake8, mypy and type annotations). Our pre-commits will help you with that.
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[boring-cyborg]

Awesome work, congrats on your first merged pull request!

[kaxil]

Well done, congratulations for your first PR 🎉