Repair pip install step in arviz workflow

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Author: michaelosthege

.github/workflows/arviz_compat.yml

@@ -82,7 +82,7 @@ jobs:
         run: |
           conda activate pymc-test-py39
           pip uninstall arviz -y
-          pip install git+git://github.com/arviz-devs/arviz.git
+          pip install git+https://github.com/arviz-devs/arviz
       - name: Run tests
         run: |
           python -m pytest -vv --cov=pymc --cov-report=xml --cov-report term --durations=50 $TEST_SUBSET