Bump actions/checkout from 2 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v3)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/hassfest.yml

@@ -8,5 +8,5 @@ jobs:
   validate:
     runs-on: "ubuntu-latest"
     steps:
-      - uses: "actions/checkout@v2"
+      - uses: "actions/checkout@v3"
       - uses: home-assistant/actions/hassfest@master