workflow: use upload-pages-artifact v3

Author: KtorZ

.github/workflows/continuous-integration.yml

@@ -47,7 +47,7 @@ jobs:
         run: aiken docs -o docs
 
       - name: 📦 Upload artifact
-        uses: actions/upload-pages-artifact@v4
+        uses: actions/upload-pages-artifact@v3
         with:
           path: "docs/"