chore(deps): update github artifact actions

Author: renovate[bot]

.github/workflows/build-antora.yml

@@ -59,7 +59,7 @@ jobs:
         run: npx antora generate --log-failure-level warn ${{ inputs.playbook-file }}
 
       - name: Upload built site
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: antora-site
           path: build/site

.github/workflows/deploy-docs.yml

@@ -27,7 +27,7 @@ jobs:
 
     steps:
       - name: Download built site
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v7
         with:
           name: antora-site
           path: build/site