Install Ansible with apt in Ubuntu workflows

We were having problems with the python-setup action when trying to use
Ubuntu 24.04 because it uses Python 3.12 instead of Python 3.8 and
because the way to install ansible with pip has changed over the years.

So we're now installing ansible with apt, just like we do in Debian
workflows. This will also install the python3 package if it isn't
already installed.

.github/workflows/ubuntu.yml

@@ -18,15 +18,10 @@ jobs:
         rails_env: [staging, production]
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-python@v2
-        with:
-          python-version: 3.8
       - name: Update system packages
         run: sudo apt-get update -y
-      - name: Install OpenSSH
-        run: sudo apt-get install -y openssh-server
-      - name: Install Ansible
-        run: pip3 install ansible
+      - name: Install needed packages
+        run: sudo apt-get install -y openssh-server ansible
       - name: Create hosts file
         run: echo "localhost ansible_connection=local ansible_user=root" > hosts
       - name: Generate dummy SSH key