Need to use github now for CI

Author: rocky

.github/workflows/ubuntu.yml

@@ -24,7 +24,7 @@ jobs:
         python -m pip install pytest
         # Can comment out when next Mathics core and Mathics-scanner are released
         # python -m pip install -e git+https://github.com/Mathics3/mathics-scanner#egg=Mathics-Scanner[full]
-        # python -m pip install -e git+https://github.com/Mathics3/mathics-core#egg=Mathics3[full]
+        python -m pip install -e git+https://github.com/Mathics3/mathics-core#egg=Mathics3[full]
         python -m pip install -e .
         # (cd src/mathics3 && bash ./admin-tools/make-op-tables.sh)
     - name: install pymathics graph