Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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/Benchmark.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     if: contains(github.event.pull_request.labels.*.name, 'run benchmark')
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@latest
       - name: Cache artifacts
         uses: actions/cache@v4

.github/workflows/UnitTest.yml

@@ -20,7 +20,7 @@ jobs:
             julia-version: '1'
             julia-arch: x86
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: "Set up Julia"
         uses: julia-actions/setup-julia@v1