chore: drop python 3.9 support (#629)

* drop python 3.9 support

* update lock file

Author: CFenner

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: ["3.9", "3.10", "3.11", "3.12"]
+        python: ["3.10", "3.11", "3.12"]
     steps:
       - name: ⤵️ Check out code from GitHub
         uses: actions/checkout@v5.0.0

mypy.ini

@@ -1,5 +1,5 @@
 [mypy]
-python_version = 3.9
+python_version = 3.10
 warn_return_any = True
 warn_unused_configs = True
 exclude = setup\.py$|build/