CI: Update actions/cache in nightly run to v4 (#15933)

Author: Ayesh

.github/workflows/nightly.yml

@@ -24,7 +24,7 @@ jobs:
           # the correct commit hashes.
           fetch-depth: 0
       - name: Grab the commit mapping
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: branch-commit-cache.json
           # The cache key needs to change every time for the