Drop redundant virtualenv we're not using

I'm guessing the expectation here was that sourceing the virtualenv
would persist, however that's not how Github Actions works. As is
therefore working fine without a virtualenv, drop the redundant work.

.github/workflows/test.yml

@@ -21,17 +21,6 @@ jobs:
         with:
           python-version: ${{ matrix.python }}
 
-      - name: Create virtualenv
-        run: python3 -m venv venv
-
-      - uses: actions/cache@v3
-        with:
-          path: venv/
-          key: ${{ runner.os }}-${{ matrix.python }}-pip-${{ hashFiles('requirements.txt') }}-${{ hashFiles('requirements-dev.txt') }}
-
-      - name: Use virtualenv
-        run: source venv/bin/activate
-
       - name: Install dependencies
         run: pip install -r requirements.txt -r requirements-dev.txt