feat(github-action)!: Update actions/checkout action to v3 (#4)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/checkout](https://togithub.com/actions/checkout) | action |
major | `v2` -> `v3` |

---

### Release Notes

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

###
[`v3`](https://togithub.com/actions/checkout/blob/HEAD/CHANGELOG.md#v353)

[Compare Source](https://togithub.com/actions/checkout/compare/v2...v3)

- [Fix: Checkout fail in self-hosted runners when faulty submodule are
checked-in](https://togithub.com/actions/checkout/pull/1196)
- [Fix typos found by
codespell](https://togithub.com/actions/checkout/pull/1287)
- [Add support for sparse
checkouts](https://togithub.com/actions/checkout/pull/1369)

</details>

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.github/workflows/fly-deploy.yaml

@@ -17,7 +17,7 @@ jobs:
     name: Deploy app
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2
+      - uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3
       - uses: superfly/flyctl-actions/setup-flyctl@master
         with:
           version: 0.1.54