CI: Display Sphinx version after populating test matrix slot

Author: amotl

.github/workflows/main.yml

@@ -68,6 +68,9 @@ jobs:
         # Install specific Sphinx version, according to test matrix slot.
         uv pip install 'sphinx==${{ matrix.sphinx-version }}'
 
+        # Display Sphinx version.
+        sphinx-build --version
+
     - name: Run linter and software tests
       run: |
         poe check