ci(deps): bump dorny/paths-filter from 3.0.2 to 4.0.1

v4.0.0 moves the action runtime to Node 24, which GitHub-hosted
`ubuntu-latest` runners support natively. v4.0.1 additionally
adds `merge_group` event support (no-op for this project). The
`action.yml` diff also introduces an optional
`predicate-quantifier` input that defaults to `'some'` — the same
matching semantics the three filters currently relied on — so
`steps.changes.outputs.{root_docs,docs,python_files}` continue to
fire identically.

Tag: https://github.com/dorny/paths-filter/tree/v4.0.1
Changelog: https://github.com/dorny/paths-filter/blob/master/CHANGELOG.md

Author: tony

.github/workflows/docs.yml

@@ -20,7 +20,7 @@ jobs:
       - uses: actions/checkout@v6
 
       - name: Filter changed file paths to outputs
-        uses: dorny/paths-filter@v3.0.2
+        uses: dorny/paths-filter@v4.0.1
         id: changes
         with:
           filters: |