ci(deps): bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 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/v4...v6)

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

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

.github/workflows/sync-main-to-earlgrey-hwe.yml

diff --git a/.github/workflows/sync-main-to-earlgrey-hwe.yml b/.github/workflows/sync-main-to-earlgrey-hwe.yml
index 884c3ef..1cb0a1a 100644
--- a/.github/workflows/sync-main-to-earlgrey-hwe.yml
+++ b/.github/workflows/sync-main-to-earlgrey-hwe.yml
@@ -11,7 +11,7 @@
     runs-on: ubuntu-latest
     steps:
       - name: Checkout the earlgrey-hwe branch
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           ref: earlgrey-hwe
           fetch-depth: 0 # Fetches all history so branches can be compared