Improve examples of using parquet reader to be more concise

[alamb]

if the follow up about the fourth pattern is needed, i/we can handle that aswell

I am not quite sure what you mean by this

Sorry i meant i can improve the examples if needed

That would be great if you have the time -- specifically I think applying both these comments to all the examples would improve the readability 🙏

• docs(parquet): add example for preserving dictionary encoding #9116 (comment)
• docs(parquet): add example for preserving dictionary encoding #9116 (comment)

Originally posted by @alamb in #9116 (comment)

[AndreaBozzo]

take