Bump actions/checkout from 5 to 6 (#274)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/cron-release.yml

@@ -14,7 +14,7 @@ jobs:
       contents: write
     steps:
       - name: 'Checkout pulp-ui (main)'
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           ref: 'main'
           fetch-depth: 128

.github/workflows/cypress.yml

@@ -22,7 +22,7 @@ jobs:
 
     steps:
       - name: 'Checkout pulp-ui (${{ github.ref }})'
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: 'backend setup'
         run: |

.github/workflows/pr-checks.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 'Checkout pulp-ui (${{ github.ref }})'
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: 'Install node 22'
         uses: actions/setup-node@v6
@@ -61,7 +61,7 @@ jobs:
       # need to checkout out head, the merge commit won't have any merges in history
       # also need more than 1 commit, assuming no PR will have more than 128
       - name: 'Checkout pulp-ui HEAD'
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 128
           ref: ${{ github.event.pull_request.head.sha }}