Update actions/cache action to v5

Author: renovate[bot]

.github/workflows/firebase_functions.yml

@@ -17,7 +17,7 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: 18.x
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: ~/.npm
           key: npm-${{ hashFiles('firebase/functions/package-lock.json') }}