config: update actions/upload-pages-artifact to v4

Author: cowwoc

.cat/issues/v2/v2.1/update-github-actions-versions/STATE.md

@@ -1,6 +1,7 @@
 # State
 
-- **Status:** open
-- **Progress:** 0%
+- **Status:** closed
+- **Progress:** 100%
 - **Dependencies:** []
-- **Blocks:** []
+- **Blocks:** []
+- **Target Branch:** v2.1

.github/workflows/pages.yml

@@ -30,7 +30,7 @@ jobs:
         uses: actions/configure-pages@v4
 
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@v4
         with:
           path: 'docs'