ci: 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-publish.yml

@@ -29,7 +29,7 @@ jobs:
     if: (github.event_name == 'schedule' && github.repository == 'nginx-proxy/acme-companion') || (github.event_name != 'schedule')
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/dockerhub-description.yml

@@ -18,7 +18,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Docker Hub Description
         uses: peter-evans/dockerhub-description@v5

.github/workflows/test.yml

@@ -29,7 +29,7 @@ jobs:
 
     steps:
       - name: Checkout Code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Build Image
         run: docker build -t "$IMAGE" .
@@ -58,7 +58,7 @@ jobs:
 
     steps:
       - name: Checkout Docker official images tests
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: docker-library/official-images
           path: official-images
@@ -116,7 +116,7 @@ jobs:
 
     steps:
       - name: Checkout Code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       # PREPARE RUNNER ENV
       - name: Add Test Domains in /etc/hosts