pipeline: disable caching of virtual environment (did not reduce runtime)

partially reverts https://github.com/fphammerle/ical2vdir/commit/1651baee4c594b11574687fd54b9ca254f57bbb2

.github/workflows/python.yml

@@ -21,9 +21,7 @@ jobs:
     - uses: actions/setup-python@v2.3.0
       with:
         python-version: ${{ matrix.python-version }}
-        # > Post Run actions/setup-python@v2.3.0
-        # > Post job cleanup.
-        # > Error: Unexpected end of JSON input
+        # did not reduce runtime of `pipenv install` (still approx. 1 min)
         #cache: pipenv
     - run: pip install --upgrade pipenv==2020.8.13
     - run: pipenv install --python "$PYTHON_VERSION" --deploy --dev
@@ -47,11 +45,8 @@ jobs:
     - uses: actions/setup-python@v2.3.0
       with:
         python-version: ${{ matrix.python-version }}
-        # > [...] uses its hash as a part of the cache key.
-        # https://github.com/actions/setup-python/tree/v2.3.0#caching-packages-dependencies
-        # > Cache saved with the key: setup-python-Linux-python-3.6.15-pipenv-bae2765561[...]
-        # > Cache saved with the key: setup-python-Linux-python-3.7.12-pipenv-bae2765561[...]
-        cache: pipenv
+        # did not reduce runtime of `pipenv install` (still approx. 1 min)
+        #cache: pipenv
     - run: pip install --upgrade pipenv==2020.8.13
     # by default pipenv picks the latest version in PATH
     - run: pipenv install --python "$PYTHON_VERSION" --deploy --dev