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/ci.yml

@@ -11,7 +11,7 @@ jobs:
       with:
         java-version: 8
         distribution: temurin
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - run: ./setup.sh
     - run: ~/.conscript/bin/cs --version
   setup_script_windows:
@@ -22,7 +22,7 @@ jobs:
       with:
         java-version: 8
         distribution: temurin
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - run: Powershell.exe -File setup.ps1
     - shell: cmd
       run: "%HOMEDRIVE%%HOMEPATH%\\.conscript\\bin\\cs --version"
@@ -40,7 +40,7 @@ jobs:
       with:
         java-version: "${{ matrix.java }}"
         distribution: temurin
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: coursier/cache-action@v7
     - uses: sbt/setup-sbt@v1
     - run: sbt -v test
@@ -56,7 +56,7 @@ jobs:
       with:
         java-version: 8
         distribution: temurin
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 10
     - uses: coursier/cache-action@v7