ci: bump actions/checkout from 5 to 6 in the actions group

Bumps the actions group with 1 update: [actions/checkout](https://github.com/actions/checkout).


Updates `actions/checkout` from 5 to 6
- [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/v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
...

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

.github/workflows/nvim_ts.yml

@@ -28,9 +28,9 @@ jobs:
       NVIM: ${{ matrix.os == 'windows-latest' && 'nvim-win64\\bin\\nvim.exe' || 'nvim' }}
       NVIM_TS_DIR: nvim-treesitter
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           repository: nvim-treesitter/nvim-treesitter
           path: ${{ env.NVIM_TS_DIR }}