ci(deps): Bump dorny/paths-filter from v3.0.2 to v4

why: GitHub Actions will require Node.js 24 by June 2, 2026.
v4 updates the runtime to Node 24 with no API changes.
what:
- Update dorny/paths-filter@v3.0.2 → @v4 in docs.yml
- No filter syntax or output changes required
- Ref: https://github.com/dorny/paths-filter/releases/tag/v4.0.0

Author: tony

.github/workflows/docs.yml

@@ -21,7 +21,7 @@ jobs:
       - uses: actions/checkout@v6
 
       - name: Filter changed file paths to outputs
-        uses: dorny/paths-filter@v3.0.2
+        uses: dorny/paths-filter@v4
         id: changes
         with:
           filters: |