Update actions/setup-python action to v6

Author: renovate[bot]

.github/workflows/documentation.yaml

@@ -18,7 +18,7 @@ jobs:
       with:
         tflint_version: v0.38.1
     - uses: actions/checkout@v3
-    - uses: actions/setup-python@v4
+    - uses: actions/setup-python@v6
     - uses: pre-commit/[email protected]
       # pre-commit fails if it changed files
       # we want to go on