fix: remove Python 3.8 and 3.9 from integration test matrix

The codebase requires Python 3.10+ due to the use of pattern matching
(match/case statements) in src/nutrient_dws/file_handler.py. This commit
aligns the integration test matrix with the project's Python version
requirements specified in pyproject.toml.

This fixes CI failures where Python 3.8/3.9 would encounter syntax errors
when trying to import modules that use Python 3.10+ features.

Author: jdrhyne

.github/workflows/ci.yml

@@ -74,7 +74,7 @@ jobs:
       (github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name == github.repository)
     strategy:
       matrix:
-        python-version: ['3.8', '3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.10', '3.11', '3.12']
 
     steps:
     - uses: actions/checkout@v4