Upgrade to actions/cache@v4 (#355)

Author: debonte

.github/workflows/test.yml

@@ -17,7 +17,7 @@ jobs:
           python-version: "3.11"
 
       - name: Cache pip
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ~/.cache/pip
           key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}