In the process of updating the documentation for another issue, I noticed that unlike the rest of the shutil doc (and the Python docs in general, not to mention those of virtually every Python package), all the functions in the [Archiving operations section](https://docs.python.org/3/library/shutil.html#archiving-operations) uses the old style, difficult to parse nested-bracket notation for the function signatures, rather then the modern style displaying them as they would be expected to appear in Python code, with clearly and explicitly indicated defaults.

Therefore, given all bracketed items are keyword arguments with defaults, and there are no cases more complex then the standard linearly-nested brackets, is there a particular reason why this was retained? Otherwise, I can go ahead and submit a PR to update this.