Bump actions/checkout from 5 to 6 (#42)

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/docker-publish.yml

@@ -51,7 +51,7 @@ jobs:
     steps:
       - # https://github.com/actions/checkout
         name: Clone git repo
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - # https://github.com/docker/metadata-action
         name: Extract git metadata for Docker image

.github/workflows/maven-publish.yml

@@ -27,7 +27,7 @@ jobs:
     steps:
       # https://docs.github.com/en/actions/use-cases-and-examples/building-and-testing/building-and-testing-java-with-maven
       # https://github.com/actions/setup-java
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Set up JDK
         uses: actions/setup-java@v5
         with:

.github/workflows/maven-verify.yml

@@ -58,7 +58,7 @@ jobs:
     steps:
       - # https://github.com/actions/checkout
         name: Clone repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - # https://github.com/ikalnytskyi/action-setup-postgres
         # copied from FDP develop (3ff9f64) build.yml