ci: bump actions/checkout from 3 to 4 (#5650)

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v3...v4)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/flatpak.yml

@@ -24,7 +24,7 @@ jobs:
       RYUJINX_VERSION: "${{ inputs.ryujinx_version }}"
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           path: Ryujinx
 
@@ -38,7 +38,7 @@ jobs:
         run: |
           echo "git_hash=$(git rev-parse HEAD)" >> $GITHUB_OUTPUT
 
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: flathub/org.ryujinx.Ryujinx
           token: ${{ secrets.RYUJINX_BOT_PAT }}