Remove Python 3.9 from test matrix due to dependency constraints

Co-authored-by: sophiagavrila <57912010+sophiagavrila@users.noreply.github.com>

Author: Copilot

.github/workflows/pytest.yaml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
 
     steps:
     - uses: actions/checkout@v5