Update unittests.yml

Author: jan-janssen

.github/workflows/unittests.yml

@@ -43,11 +43,6 @@ jobs:
           label: linux-64-py-3-10
           prefix: /usr/share/miniconda3/envs/my-env
 
-        - operating-system: ubuntu-latest
-          python-version: '3.9'
-          label: linux-64-py-3-9
-          prefix: /usr/share/miniconda3/envs/my-env
-
     steps:
     - uses: actions/checkout@v4
     - name: Merge conda environment