chore(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](actions/checkout@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>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -14,18 +14,18 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout this repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: webhook
 
       - name: Checkout web4 (sibling protocol repo)
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: TeoSlayer/pilotprotocol
           path: web4
 
       - name: Checkout common
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: pilot-protocol/common
           path: common