Bump actions/checkout from 5 to 6

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] <support@github.com>

Author: dependabot[bot]

.github/workflows/publish_master.yml

@@ -13,7 +13,7 @@ jobs:
     name: Publish master image
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Build
       run: |
         GITHUB_REPOSITORY_LC=$(echo "${GITHUB_REPOSITORY}" | tr [A-Z] [a-z])

.github/workflows/publish_stable.yml

@@ -10,7 +10,7 @@ jobs:
     name: Publish stable image
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Build
       run: |
         GITHUB_REPOSITORY_LC=$(echo "${GITHUB_REPOSITORY}" | tr [A-Z] [a-z])

.github/workflows/testing.yml

@@ -19,7 +19,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up Python
         uses: actions/setup-python@v6
@@ -48,7 +48,7 @@ jobs:
     name: Test run action
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: ./
       with:
         path: test/testdata
@@ -58,7 +58,7 @@ jobs:
     name: Check for spelling errors
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: ./
       with:
         check_filenames: true
@@ -86,7 +86,7 @@ jobs:
         include:
           - codespell_pip_version: 'git+https://github.com/codespell-project/codespell.git'
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v6
       - run: pip3 --quiet --quiet install ${{ matrix.codespell_pip_version }}