github: update upload-artifact action

This removes the warnings about Node 10 deprecation in the GitHub CI.

Signed-off-by: David Bauer <mail@david-bauer.net>

.github/workflows/build-docs.yml

@@ -23,7 +23,7 @@ jobs:
       - name: Build documentation
         run: make -C docs html
       - name: Archive build output
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: docs_output
           path: docs/_build/html

.github/workflows/build-gluon.yml

@@ -56,13 +56,13 @@ jobs:
 
       - name: Archive build logs
         if: ${{ !cancelled() }}
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: ${{ matrix.target }}_logs
           path: openwrt/logs
 
       - name: Archive build output
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: ${{ matrix.target }}_output
           path: output