gci: Update apt before installing

A stale apt-get cache could otherwise cause a test failure.

.github/workflows/ci.yaml

@@ -166,6 +166,7 @@ jobs:
       - name: Install dependencies
         run: |
           bash -x .github/scripts/setup.sh
+          sudo apt-get update -qq
           sudo apt-get install -y -qq lowdown
           pip install -U pip wheel poetry
           # Export and then use pip to install into the current env