Set minimum supported version to Python 3.10+

Following [SPEC 0](https://scientific-python.org/specs/spec-0000/) policy where Python 3.9 should be dropped in 2024 quarter 4.

Author: weiji14

.github/workflows/pypi-release.yaml

@@ -28,7 +28,7 @@ jobs:
       - uses: actions/setup-python@v4
         name: Install Python
         with:
-          python-version: 3.8
+          python-version: "3.10"
 
       - name: Install dependencies
         run: |

pyproject.toml

@@ -8,7 +8,7 @@ description = "Interface for using cupy in xarray, providing convenience accesso
 authors = [{name = "cupy-xarray developers"}]
 license = {text = "Apache License"}
 readme = "README.md"
-requires-python = ">=3.8"
+requires-python = ">=3.10"
 classifiers = [
     "Programming Language :: Python :: 3",
     "Operating System :: OS Independent",