fix typo

Author: Joseph-Edwards

.github/workflows/tests.yml

@@ -52,7 +52,7 @@ jobs:
           pip3 --version
       - name: "Pip3 installing libsemigroups_pybind11 . . ."
         run: |
-          CXX="${{ matrix.compiler }}"pip3 install . -v
+          CXX="${{ matrix.compiler }}" pip3 install . -v
       - name: "python -m pytest -vv tests/test_*.py . . ."
         run: |
           python -m pytest -vv tests/test_*.py