Correct the syntax for the !contains statement (take 2)

Author: BTSpeake

.github/workflows/ci-testing.yml

@@ -36,7 +36,7 @@ jobs:
         run: pytest --cov=aiidalab_alc --cov-report xml:coverage.xml
 
       - name: Run the test suite without coverage 
-        if:  ! contains(matrix.python-version, '3.12')
+        if:  ${{ !contains(matrix.python-version, '3.12') }}
         run: pytest 
 
       - name: Report coverage to Coveralls