Add pytest dependency installation to CI workflow

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install -r space2stats_api/src/requirements.txt
-        pip install pre-commit
+        pip install pre-commit pytest
 
     - name: Set PYTHONPATH
       run: echo "PYTHONPATH=$(pwd)/space2stats_api" >> $GITHUB_ENV