chore(gha): bump actions/upload-artifacts from 4 to 6

Author: duncdrum

.github/workflows/build.yml

@@ -70,15 +70,15 @@ jobs:
 
       - name: upload xar package
         if: ${{ matrix.java-version == 21 }}
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: frus-xar
           path: build/*.xar
           if-no-files-found: ignore
 
       - name: upload smoke test
         if: ${{ matrix.java-version == 21 }}
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: frus-bats
           path: tests/bats/
@@ -163,7 +163,7 @@ jobs:
         if: always()
         run: docker cp exist:/exist/logs .
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         if: always()
         with:
           name: exist_${{ matrix.exist-version }}_logs