ci: install system deps for lxml in test job (ensure lxml builds)

Author: Sahil-u07

.github/workflows/ci.yml

@@ -43,6 +43,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
+          sudo apt-get update && sudo apt-get install -y libxml2-dev libxslt1-dev python3-dev build-essential
           pip install -r requirements-ci.txt
 
       - name: Run tests