chore(deps): Bump actions/checkout from 4 to 6 (#558)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Jesse Wright <63333554+jeswr@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/automerge.yml

@@ -13,7 +13,7 @@ jobs:
       repository-projects: write
     if: github.actor == 'dependabot[bot]'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - run: gh pr merge ${{ github.event.pull_request.html_url }} --auto --squash
       - run: gh pr review ${{ github.event.pull_request.html_url }} --approve
     env:

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - run: npm ci --ignore-scripts
       - run: npm run build
       - run: npm run test
@@ -34,7 +34,7 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - run: npm ci --ignore-scripts
       - run: npm run build
       - run: npm run lint
@@ -51,14 +51,14 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - run: npm ci
       - run: npm run spec-${{ matrix.spec }}
 
   docs:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: 24.x
@@ -116,7 +116,7 @@ jobs:
       pull-requests: write
       id-token: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: 24.x