[CI] declares requires python 3.9 and remove stale files

[pablo-estevez-lrn]

• Declare a minimum supported Python version of 3.9 so pip don't update this package to newer versions if the python version is 3.8 or less(as is not tested on that version)
• Removed setup-cfg declaration of universal, that was publishing python2 wheels, that were unusable as we are not using universal syntax.
• Removed manifest.in that was referencing files that doesn't exists anymore, and logging a warning.

Checklist

• Feature

• Bug

• Security

• Documentation

• ChangeLog.md updated

• Tests added

• All testsuites passed

• make dist completed successfully

• Bump package version if release coming

[Copilot]

🟢 Approval recommended

The packaging metadata and build changes consistently enforce the tested Python support range.

0 open findings

What changed in this PR

Declares Python 3.9 as the minimum supported version and cleans obsolete packaging configuration.

Changes:

• Adds python_requires >=3.9.
• Produces Python 3-only wheels.
• Removes stale manifest entries and documents the support change.

File	Description
setup.py	Declares Python 3.9 minimum.
setup.cfg	Removes universal-wheel configuration.
MANIFEST.in	Removes references to nonexistent files.
Makefile	Builds non-universal wheels.
ChangeLog.md	Records the Python requirement.

🧠 Review effort: Balanced

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