[ci] Pinned django-x509

Author: pandafy

.github/workflows/ci.yml

@@ -76,7 +76,7 @@ jobs:
         pip install -U pip wheel setuptools
         pip install -U -r requirements-test.txt
         pip install -U -e .
-        pip install -UI "openwisp-users @ https://github.com/openwisp/openwisp-users/tarball/issues/238-view-shared-objects"
+        pip install -UI "openwisp-users @ https://github.com/openwisp/openwisp-users/tarball/issues/238-view-shared-objects" "django-x509 @ https://github.com/openwisp/django-x509/tarball/1.3"
         pip install ${{ matrix.django-version }}
 
     - name: Start postgres and redis