build(deps): bump actions/checkout in the gha-dependencies group

Bumps the gha-dependencies 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](actions/checkout@v5...v6)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/dependabot_changelog_update.yml

@@ -20,7 +20,7 @@ jobs:
           owner: ${{ github.repository_owner }}
           repositories: "go-fastly"
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           token: ${{ steps.github-token.outputs.token }}
           repository: ${{ github.event.pull_request.head.repo.full_name }}

.github/workflows/pr_test.yml

@@ -20,7 +20,7 @@ jobs:
     name: lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-go@v6
         with:
           go-version: 1.24.x
@@ -34,7 +34,7 @@ jobs:
     continue-on-error: true
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Setup Go
         uses: actions/setup-go@v6
         with:
@@ -60,7 +60,7 @@ jobs:
     runs-on: ${{ matrix.platform }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install Go
         uses: actions/setup-go@v6
         with: