Reinserting python -m pip install -e . in tests-linux.yml.

.github/workflows/tests-linux.yml

@@ -37,7 +37,7 @@ jobs:
         shell: bash -l {0}
         run: |
           python -m pip install -U pip
-          # python -m pip install -e .
+          python -m pip install -e .
           pip install pytest pytest-cov
           sudo apt install lcov