Update actions/setup-python action to v6 (#16)

Co-authored-by: thecluster-bot[bot] <98929874+thecluster-bot[bot]@users.noreply.github.com>

Author: thecluster-bot[bot]

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
           fetch-depth: 0
 
       # Required by yamale and yamllint
-      - uses: actions/setup-python@v5.6.0
+      - uses: actions/setup-python@v6.0.0
         with:
           python-version: '3.x'