ci: install libssh-dev

This started to be needed for some reason.

Author: pbrezina

.github/workflows/ci.yml

@@ -25,6 +25,9 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
+        sudo apt-get update
+        sudo apt-get install -y libssh-dev
+
         python -m pip install --upgrade pip
         pip install tox tox-gh
     - name: Prepare tox environment and install packages