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] <[email protected]>

Author: dependabot[bot]

.github/workflows/build_docs.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       # checkout the repository
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       # setup Python
       - name: Install Python

.github/workflows/deploy_docs.yml

@@ -30,7 +30,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Setup Pages
         uses: actions/configure-pages@v5

.github/workflows/docker-image.yml

@@ -25,7 +25,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3

.github/workflows/pre-commit.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       # This action sets the current path to the root of your github repo
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Install Python
         uses: actions/setup-python@v6

.github/workflows/reproduce_results.yml

@@ -22,7 +22,7 @@ jobs:
       RESULTDIR: ./artifacts/results
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
     # setup Python
       - name: Install Python