removing from documentation deprecated python3-distutils

[tiamilani]

Description

Removing deprecated for python3.12 (ubuntu 24.04) python3-distutils from the compiling documentation.
Substituted with python3-setuptools as described in the documentation [1-2].

Added a note to explain the presence of setuptools instead of distutils.

[1] https://docs.python.org/3.10/library/distutils.html
[2] https://peps.python.org/pep-0632/

Fixes # (issue)

No corresponding issue

Testing

No tests executed

Checklist

• My code follows the style guidelines of this project
• My changes generate no new warnings
• My code also compiles for cuda_* and llvm_* variants. If you can't test this, please leave below
• I have commented my code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I cleaned the commit history and removed any "Merge" commits
• I give permission that the Mitsuba 3 project may redistribute my contributions under the terms of its license