Bump actions/checkout from 5 to 6 (#548)

Bumps [actions/checkout](https://github.com/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
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci-format.yml

@@ -12,7 +12,7 @@ jobs:
     name: Format
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: actions/setup-python@v6
       with:
         python-version: '3.10'

.github/workflows/reusable-sphinx-check-single-version.yml

@@ -17,7 +17,7 @@ jobs:
   build-single-version:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         repository: ros-controls/control.ros.org
         ref: humble

.github/workflows/sphinx-check-links-pr.yml

@@ -7,7 +7,7 @@ jobs:
   check-links:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
     - uses: actions/setup-python@v6

.github/workflows/sphinx-check-links.yml

@@ -13,7 +13,7 @@ jobs:
       matrix:
         BRANCH: [humble]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
         ref: ${{ matrix.BRANCH }}

.github/workflows/sphinx-check-page-multiversion.yml

@@ -22,7 +22,7 @@ jobs:
   build-multiversion:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
     - uses: actions/setup-python@v6

.github/workflows/sphinx-check-warnings-pr.yml

@@ -7,7 +7,7 @@ jobs:
   build-singleversion-halt-on-warnings:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
     - uses: actions/setup-python@v6

.github/workflows/sphinx-check-warnings.yml

@@ -13,7 +13,7 @@ jobs:
       matrix:
         BRANCH: [humble]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
         ref: ${{ matrix.BRANCH }}