V3 also install streamlit-folium itself

Author: hansthen

.github/workflows/test_streamlit_folium.yml

@@ -48,4 +48,5 @@ jobs:
     - name: Test with pytest and retry flaky tests up to 3 times
       run: |
         cd streamlit_folium
+	pip install streamlit-folium
         pytest tests/test_frontend.py --browser chromium -s --reruns 3 --junit-xml=test-results.xml