Unify use of typing module imports

[j2kun]

Decide whether to use, e.g, list(int) or List[int] from typing. And make it consistent across all tips and solution code in the chapters.

[Josde]

For added info, just in case someone wants to take a look at this, PEP 585 recommends list[int] over typing.List[int], as the latter syntax is deprecated and may be deleted in the future.

thanks for the book, by the way!