ci: Fix Windows pip issues

Author: dbanty

.github/workflows/checks.yml

@@ -27,12 +27,12 @@ jobs:
         path: .venv
         key: ${{ runner.os }}-${{ matrix.python }}-dependencies-${{ hashFiles('**/poetry.lock') }}
         restore-keys: |
-          ${{ runner.os }}-${{ matrix.python }}-dependencies-
+          ${{ runner.os }}-${{ matrix.python }}-dependencies-v2
     - name: Install dependencies
       run: |
         pip install poetry
         poetry config virtualenvs.in-project true
-        poetry run pip install --upgrade pip
+        poetry run python -m pip install --upgrade pip
         poetry install
 
     - name: Run Black