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/mkdocs-dryrun.yml

@@ -18,7 +18,7 @@ jobs:
       # Checkout repository including submodules
       - name: Checkout
         id: checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: true
 

.github/workflows/mkdocs.yml

@@ -28,7 +28,7 @@ jobs:
       # Checkout repository including submodules
       - name: Checkout
         id: checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: true
 

.github/workflows/publish.yml

@@ -10,7 +10,7 @@ jobs:
   deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: true
       - name: Set up Python

.github/workflows/python-app.yml

@@ -31,7 +31,7 @@ jobs:
         os: ['ubuntu-latest', 'windows-latest', 'macos-latest']
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         submodules: 'recursive'
     - name: Set up Python
@@ -68,7 +68,7 @@ jobs:
   Lint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         submodules: 'recursive'
     - name: Set up Python
@@ -89,7 +89,7 @@ jobs:
   Type-check:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         submodules: 'recursive'
     - name: Set up Python