Update .gitlab-ci.yml

pip3 install -U to avoid permission right

.gitlab-ci.yml

@@ -22,7 +22,7 @@ build:
 test:
   script:
   #- python3 setup.py test
-  - pip3 install tox flake8  # you can also use tox
+  - pip3 -U install tox flake8  # you can also use tox
   - tox -e py36,flake8
   - python -m unittest discover navipy