github_actions: remove tox parallel

Sometimes, when running tox parallel on Github Actions, it fails on the
Windows runners with 'Action Denied' to write a wheel file in the pip
cache.

Change-Id: Ifc1f4edf1cb1bfef97e5ced20eeada22b9eddc4a
Signed-off-by: Adrian Vladu <[email protected]>

Author: ader1990

.github/workflows/cloudbase_init_tests.yml

@@ -53,7 +53,7 @@ jobs:
     - name: Run Cloudbase-Init unit tests with tox
       shell: cmd
       run: |
-        tox run-parallel --parallel-live --parallel-no-spinner -e py3,pep8
+        tox -e py3,pep8
   windows-functional-tests:
     runs-on: windows-latest
     strategy: