Try to fix GH actions syntax (#355)

.github/workflows/ci.yml

@@ -75,12 +75,13 @@ jobs:
           python -m unittest test_typing_extensions.py
 
       - name: Test CPython typing test suite
+        # Test suite fails on PyPy even without typing_extensions
+        if: ${{ !startsWith(matrix.python-version, 'pypy') }}
         run: |
+          cd src
           # Run the typing test suite from CPython with typing_extensions installed,
           # because we monkeypatch typing under some circumstances.
           python -c 'import typing_extensions; import test.__main__' test_typing -v
-        # Test suite fails on PyPy even without typing_extensions
-        if: !startsWith(matrix.python-version, 'pypy')
 
   linting:
     name: Lint