drop py39 support, explicitly add 3.12

Author: chrishavlin

.github/workflows/run-pytest-tests.yml

@@ -9,7 +9,7 @@ jobs:
     strategy:
       matrix:
         platform: [ubuntu-latest, windows-latest, macos-latest]
-        python-version: ['3.9', '3.10', '3.11']
+        python-version: ['3.10', '3.11', '3.12']
 
     steps:
     - uses: actions/checkout@v3

pyproject.toml

@@ -9,16 +9,16 @@ authors = [
 ]
 description="interface between yt and xarray"
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 classifiers = [
     "Development Status :: 4 - Beta",
     "Intended Audience :: Developers",
     "License :: OSI Approved :: MIT License",
     "Natural Language :: English",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
 ]
 dependencies=['yt>=4.2.0', 'h5py>=3.4.0', 'pooch>=1.5.1', 'xarray']
 dynamic = ["version"]