FIX github actions backend tests not running

Trying to install libnss3-dev resulted in the archive missing from the
repo. Trying to see if running an `apt-get update` to update the apt
listings would fix it.

.github/workflows/main.yml

@@ -30,6 +30,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
+        sudo apt-get update
         sudo apt-get install -y --no-install-recommends --no-install-suggests libxmlsec1-dev libz-dev
         pip install -r requirements.txt -r requirements.dev.txt
     - name: Backend Unit Tests MariaDB