Do not qualify pip invocations in GitHub Actions workflow.

.github/workflows/lint-test-cover-docs-build-upload.yml

@@ -28,7 +28,7 @@ jobs:
           mv libsodium-1.0.18.tar.gz src/rbcl/libsodium.tar.gz
       - name: Install Python dependencies for build process.
         run: |
-          python -m pip install .[build]
+          pip install .[build]
       - name: Build wheel file.
         run: |
           mkdir tmpwheelhouse
@@ -39,10 +39,10 @@ jobs:
           cp build/lib*/rbcl/_sodium.py src/rbcl/_sodium.py
       - name: Test wheel installation.
         run: |
-          .venv/bin/pip install -f wheelhouse --no-index --force-reinstall --no-dependencies rbcl
+          pip install -f wheelhouse --no-index --force-reinstall --no-dependencies rbcl
       - name: Lint and test module (and compiled libsodium shared library file).
         run: |
-          python -m pip install -U .[lint,test]
+          pip install -U .[lint,test]
           python -m pylint rbcl src/rbcl/_sodium.tmpl src/rbcl/_sodium_build.py --disable=duplicate-code # Check against linting rules.
           python src/rbcl/rbcl.py -v # Run doctests.
           python -m pytest # Run tests.