chore(deps): 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/cvmfs_config_package.yml

@@ -8,7 +8,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: ./
       with:
         cvmfs_repositories: 'software.eessi.io'

.github/workflows/cvmfs_http_proxy.yml

@@ -8,7 +8,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: ./
       with:
         cvmfs_http_proxy: 'auto'

.github/workflows/cvmfs_repositories.yml

@@ -8,7 +8,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: ./
       with:
         cvmfs_repositories: 'grid.cern.ch'

.github/workflows/macos.yml

@@ -12,7 +12,7 @@ jobs:
       matrix:
         os: [macos-latest, macos-13]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: ./
       with:
         cvmfs_repositories: 'sft.cern.ch'

.github/workflows/ubuntu.yml

@@ -12,7 +12,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, ubuntu-22.04, ubuntu-24.04]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: ./
     - name: Test CernVM-FS
       run: |