[BLD] Update requires-python metadata to Python 3.7 (#630)

* [BLD] Update requires-python metadata to Python 3.7

* Update requires-python metadata through setuptools's python_requires
  to reflect that only Python 3.7+ is distributed on PyPI and only
  Python 3.8+ is tested in CI and so Python 3.6 is not supported.
   - c.f. https://peps.python.org/pep-0621/#requires-python
   - The use of requires-python is to provide guards to keep older
     CPython versions from installing releases that could contain
     unrunnable code.
* Python 3.6 is also EOL

┌───────┬────────────┬─────────┬────────────────┬────────────┬────────────┐
│ cycle │  release   │ latest  │ latest release │  support   │    eol     │
├───────┼────────────┼─────────┼────────────────┼────────────┼────────────┤
│ 3.12  │ 2023-10-02 │ 3.12.4  │   2024-06-06   │ 2025-04-02 │ 2028-10-31 │
│ 3.11  │ 2022-10-24 │ 3.11.9  │   2024-04-02   │ 2024-04-01 │ 2027-10-31 │
│ 3.10  │ 2021-10-04 │ 3.10.14 │   2024-03-19   │ 2023-04-05 │ 2026-10-31 │
│ 3.9   │ 2020-10-05 │ 3.9.19  │   2024-03-19   │ 2022-05-17 │ 2025-10-31 │
│ 3.8   │ 2019-10-14 │ 3.8.19  │   2024-03-19   │ 2021-05-03 │ 2024-10-31 │
│ 3.7   │ 2018-06-26 │ 3.7.17  │   2023-06-05   │ 2020-06-27 │ 2023-06-27 │
│ 3.6   │ 2016-12-22 │ 3.6.15  │   2021-09-03   │ 2018-12-24 │ 2021-12-23 │
│ 3.5   │ 2015-09-12 │ 3.5.10  │   2020-09-05   │   False    │ 2020-09-30 │
│ 3.4   │ 2014-03-15 │ 3.4.10  │   2019-03-18   │   False    │ 2019-03-18 │
│ 3.3   │ 2012-09-29 │ 3.3.7   │   2017-09-19   │   False    │ 2017-09-29 │
│ 3.2   │ 2011-02-20 │ 3.2.6   │   2014-10-12   │   False    │ 2016-02-20 │
│ 3.1   │ 2009-06-26 │ 3.1.5   │   2012-04-06   │   False    │ 2012-04-09 │
│ 3.0   │ 2008-12-03 │ 3.0.1   │   2009-02-12   │   False    │ 2009-06-27 │
│ 2.7   │ 2010-07-03 │ 2.7.18  │   2020-04-19   │   False    │ 2020-01-01 │
│ 2.6   │ 2008-10-01 │ 2.6.9   │   2013-10-29   │   False    │ 2013-10-29 │
└───────┴────────────┴─────────┴────────────────┴────────────┴────────────┘

* [DOC] Add Python 3.11 and Python 3.12 PyPI classifier metadata.

* Add Python 3.11 and Python 3.12 as PyPI trove classifiers.

Author: matthewfeickert

setup.py

@@ -70,7 +70,7 @@
     scripts=[],
     data_files=[],
     install_requires=["numpy>=1.16", "scipy>=1.6"],
-    python_requires=">=3.6",
+    python_requires=">=3.7",
     classifiers=[
         'Development Status :: 5 - Production/Stable',
         'Intended Audience :: Developers',
@@ -92,10 +92,11 @@
         'Topic :: Scientific/Engineering :: Mathematics',
         'Topic :: Scientific/Engineering :: Information Analysis',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
+        'Programming Language :: Python :: 3.11',
+        'Programming Language :: Python :: 3.12',
     ]
 )