[CI] Fix installing enchant for github docs workflow

The enchant package was renamed for version 2 to enchant-2 and original
enchant package removed in Ubuntu 22.04 so docs workflow failed

Fixed by using latest package and specifying ubuntu version to avoid
unexpected failures in future.

.github/workflows/docs.yml

@@ -36,7 +36,7 @@ jobs:
         run: |
           pip install --upgrade pip wheel
           pip install tox
-          sudo apt-get install enchant
+          sudo apt-get install enchant-2
 
       - name: Test with tox
         env: