Add testing for python 3.12 and remove for 3.9

3.12 has been out a while and 3.9 will go end of life in a few months.
Lets keep things relatively upto date.

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.9', '3.10', '3.11']
+        python-version: ['3.10', '3.11', '3.12']
 
     steps:
     - uses: actions/checkout@v3
@@ -29,7 +29,7 @@ jobs:
       run: |
         coverage run -m pytest -v && coverage xml
     - name: Upload coverage to Codecov
-      if: ${{ matrix.python-version == '3.11' }}
+      if: ${{ matrix.python-version == '3.12' }}
       uses: codecov/codecov-action@v3
       with:
         token: ${{ secrets.CODECOV_TOKEN }}