chore(deps): update actions/stale action to v9 (#355)

[![Mend
Renovate](https://app.renovatebot.com/images/banner.svg)](https://renovatebot.com)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/stale](https://togithub.com/actions/stale) | action | major |
`v8` -> `v9` |

---

### Release Notes

<details>
<summary>actions/stale (actions/stale)</summary>

### [`v9`](https://togithub.com/actions/stale/compare/v8...v9)

[Compare Source](https://togithub.com/actions/stale/compare/v8...v9)

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR has been generated by [Mend
Renovate](https://www.mend.io/free-developer-tools/renovate/). View
repository job log
[here](https://developer.mend.io/github/dooboolab-community/flutter_calendar_carousel).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNy44Ny4yIiwidXBkYXRlZEluVmVyIjoiMzcuODcuMiIsInRhcmdldEJyYW5jaCI6Im1haW4ifQ==-->

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/stale.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/stale@v8
+    - uses: actions/stale@v9
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
         days-before-stale: 90