Update actions/cache to v4

Author: bowenszhu

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
       - uses: julia-actions/setup-julia@v2
         with:
           version: 1
-      - uses: actions/cache@v1
+      - uses: actions/cache@v4
         env:
           cache-name: cache-artifacts
         with: