ci: drop Python 3.9 from test matrix

urllib3 2.7.0 raised the project floor to ^3.10, so building/testing on
3.9 no longer resolves. Bump build_package to 3.12 and drop 3.9 from the
test_package matrix.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: moshemorad

.github/workflows/test-installation.yaml

@@ -10,7 +10,7 @@ jobs:
         - name: Set up Python
           uses: actions/setup-python@v2
           with:
-            python-version: 3.9
+            python-version: 3.12
         - name: Build and install package
           run: |
             curl -sSL https://install.python-poetry.org | python3 - --version 1.8.5
@@ -31,7 +31,7 @@ jobs:
       strategy:
         fail-fast: false
         matrix:
-          python-version: ["3.9", "3.10", "3.11", "3.12"]
+          python-version: ["3.10", "3.11", "3.12"]
 
       steps:
         - name: Set up Python ${{ matrix.python-version }}