use cache v4

Author: lmiq

.github/workflows/CI.yml

@@ -23,7 +23,7 @@ jobs:
       - uses: julia-actions/setup-julia@v2
         with:
           version: ${{ matrix.version }}
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         env:
           cache-name: cache-artifacts
         with: