MNT Fix Python 3.12 deprecation warning

[lesteve]

• ast.Num is deprecated in Python 3.12
• .n is deprecated in Python 3.12 and replaced by .value

❯ ipython
Python 3.12.0 | packaged by conda-forge | (main, Oct  3 2023, 08:43:22) [GCC 12.3.0]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.16.1 -- An enhanced Interactive Python. Type '?' for help.

In [1]: import ast

In [2]: ast.Num(3)
<ipython-input-2-42ae1b59512c>:1: DeprecationWarning: ast.Num is deprecated and will be removed in Python 3.14; use ast.Constant instead
  ast.Num(3)
Out[2]: <ast.Constant at 0x7f31a30d5850>

In [3]: ast.Num(3).n
<ipython-input-3-f0830cd35b24>:1: DeprecationWarning: ast.Num is deprecated and will be removed in Python 3.14; use ast.Constant instead
  ast.Num(3).n
<ipython-input-3-f0830cd35b24>:1: DeprecationWarning: Attribute n is deprecated and will be removed in Python 3.14; use value instead
  ast.Num(3).n
Out[3]: 3

Or https://docs.python.org/3/library/ast.html#node-classes

Deprecated since version 3.8: Old classes ast.Num, ast.Str, ast.Bytes, ast.NameConstant and ast.Ellipsis are still available, but they will be removed in future Python releases. In the meantime, instantiating them will return an instance of a different class.

cc @adrinjalali who has written this code I think 😉

Context: this was seen in scikit-learn CI when turning warnings into errors scikit-learn/scikit-learn#27627

[tomMoral]

This will need to wait until we merge #1515 dropping the support of python3.7. ^^

Otherwise LGTM!

edit: the PR has been merge :)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e787de8) 95.03% compared to head (fd62768) 94.98%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1518      +/-   ##
==========================================
- Coverage   95.03%   94.98%   -0.06%     
==========================================
  Files          45       45              
  Lines        7551     7551              
==========================================
- Hits         7176     7172       -4     
- Misses        375      379       +4     

Files	Coverage Δ
joblib/_utils.py	95.45% <100.00%> (ø)

... and 5 files with indirect coverage changes

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