chore(deps): bump actions/checkout from 5 to 6 (MapleStoryUnity#29)

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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -34,7 +34,7 @@ jobs:
     name: Test all modes ✨
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           lfs: true
       - uses: actions/[email protected]
@@ -79,7 +79,7 @@ jobs:
           #- Stadia
           #- CloudRendering
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           lfs: true