Update packaging-projects.rst: rephrase first explanation of __init__.py

[wyattscarpenter]

I thought the explanation of init.py was kind of confusing, so I have improved it somewhat.

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📚 Documentation preview 📚: https://python-packaging-user-guide--1538.org.readthedocs.build/en/1538/

[abravalheri]

To be honest, that is still a weak reasoning¹.

Users can import a directory even if it does not have an __init__.py. Sure, it will not be a "regular" package, it will be a "namespace" package, but the text does not explain what is so great about regular packages and why they are recommended over namespaces.

Footnotes

1. The original text had weak reasoning. This is not a problem this PR is introducing. In that respect things are more or less the same. ↩

[wyattscarpenter]

This is true.

On the other hand, I guess most users do want a regular package, and if so then there's some virtue in glossing over the exceptions in this very early guide. (There is at least a footnote to explain what is being glossed over.)