Revert "remove cache"

This reverts commit 567908e.

Author: jinliu9508

.github/workflows/create-release-pr.yml

@@ -65,6 +65,15 @@ jobs:
           brew install gh jq || true
           gh auth status || gh auth login --with-token <<< "$GH_TOKEN"
 
+      # to save time, use cached Unity installation if available
+      - name: Cache Unity
+        uses: actions/cache@v4
+        with:
+          path: /Applications/Unity/Hub
+          key: UnityEditor-${{ runner.os }}
+          restore-keys: |
+            UnityEditor-${{ runner.os }}
+
       # setup Unity using the version file
       - name: Setup Unity
         uses: buildalon/[email protected]