gh-149035: Modernize legacy Python patterns in Doc/tutorial/stdlib2.rst

[ByteFlowing1337]

• Issue: Modernize legacy Python patterns and outdated syntax in documentation #149035

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📚 Documentation preview 📚: https://cpython-previews--149036.org.readthedocs.build/

[hugovk]

Thanks, whilst we're editing this file, please could you also edit the headers to use sentence case?

For example: "Brief Tour of the Standard Library — Part II" -> "Brief tour of the standard library — part II", "Output Formatting" -> "Output formatting", and so on?

https://devguide.python.org/documentation/style-guide/#capitalization

[ByteFlowing1337]

Thanks, whilst we're editing this file, please could you also edit the headers to use sentence case?

For example: "Brief Tour of the Standard Library — Part II" -> "Brief tour of the standard library — part II", "Output Formatting" -> "Output formatting", and so on?

https://devguide.python.org/documentation/style-guide/#capitalization

Done :)

[hugovk]

Thanks!