Drop support for Python 3.9

[ndgrigorian]

This PR proposes dropping Python 3.9 support from mkl_fft, as it has long been unsupported by NumPy

[Copilot]

Pull Request Overview

This PR removes Python 3.9 support from mkl_fft, aligning with NumPy's deprecation of this Python version. The changes update package metadata and CI/CD configurations to reflect the new minimum supported version of Python 3.10.

• Removed Python 3.9 from package classifiers and version requirements
• Updated all CI/CD workflows to exclude Python 3.9 from test matrices
• Removed conditional logic specific to Python 3.9 compatibility issues

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pyproject.toml	Removed Python 3.9 classifier and updated minimum required version to 3.10
.github/workflows/conda-package.yml	Removed Python 3.9 from test matrices and eliminated conditional scipy installation logic
.github/workflows/conda-package-cf.yml	Removed Python 3.9 entries from test matrix configurations
.github/workflows/build_pip.yaml	Removed Python 3.9 from build test matrix
.github/workflows/build-with-clang.yml	Removed Python 3.9 from clang build test matrix

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[antonwolfy]

Thank you @ndgrigorian

[ndgrigorian]

@antonwolfy
your thanks are appreciated, but an approval would be even more :)