Update linting.yml

Author: tschaume

.github/workflows/linting.yml

@@ -21,7 +21,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install -r requirements/requirements-ubuntu-latest_py{{ matrix.python-version }}_extras.txt --quiet
+        pip install -r requirements/requirements-ubuntu-latest_py${{ matrix.python-version }}_extras.txt --quiet
         python -m pip install types-requests
     - name: mypy
       run: |