build(deps): bump actions/checkout from 5 to 6 (#910)

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/build-publish-docs.yaml

@@ -34,7 +34,7 @@ jobs:
       contents: write
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: "3.11"
@@ -61,7 +61,7 @@ jobs:
     runs-on: ubuntu-24.04
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: "3.11"

.github/workflows/build-publish-helm-chart.yaml

@@ -20,7 +20,7 @@ jobs:
       packages: write
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           # chartpress requires git history to set chart version and image tags
           # correctly

.github/workflows/build-publish-python-packages.yaml

@@ -69,7 +69,7 @@ jobs:
             upload_sdist: false
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-go@v6
         with:
           go-version: "1.23"

.github/workflows/refreeze-dockerfile-requirements-txt.yaml

@@ -29,7 +29,7 @@ jobs:
           - image: dask-gateway-server
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Refreeze Dockerfile.requirements.txt based on Dockerfile.requirements.in
         run: |

.github/workflows/test.yaml

@@ -67,7 +67,7 @@ jobs:
             go-version: "1.23"
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: "${{ matrix.python-version }}"
@@ -155,7 +155,7 @@ jobs:
           - k3s-channel: stable
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           # chartpress requires git history to set chart version and image tags
           # correctly
@@ -316,7 +316,7 @@ jobs:
           - slurm
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Login to ghcr.io read access to CI image
         run: echo "${{ secrets.github_token }}" | docker login ghcr.io -u $ --password-stdin