build(deps): Bump actions/checkout from 2 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...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/build.yml

@@ -11,7 +11,7 @@ jobs:
       matrix:
         java: [ "8", "11" ] # 16?
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v6
 
       - name: Set up JDK ${{ matrix.java }}
         uses: actions/setup-java@v2

.github/workflows/release.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     if: "!contains(github.event.head_commit.message, '[ci skip]') && !contains(github.event.head_commit.message, '[skip ci]')"
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0