Fix CI: add httpx to test deps (stale cache)

.gitlab-ci.yml

@@ -19,7 +19,7 @@ test:
     - source .venv/bin/activate
     - pip install --upgrade pip
     - pip install -r requirements.txt
-    - pip install pytest pytest-asyncio
+    - pip install pytest pytest-asyncio httpx
   script:
     - source .venv/bin/activate
     - python3 -m pytest tests/ -v --tb=short