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.

Release notes: https://github.com/dorny/paths-filter/releases/tag/v4.0.0
               https://github.com/dorny/paths-filter/releases/tag/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: |