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/test.yaml

@@ -28,7 +28,7 @@ jobs:
         enable-cache: ['true', 'false']
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install devbox
         uses: ./
         with:
@@ -42,7 +42,7 @@ jobs:
       matrix:
         enable-cache: ['true', 'false']
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install devbox
         uses: ./
         with:
@@ -54,7 +54,7 @@ jobs:
   test-action-with-sha256-checksum:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install devbox
         uses: ./
         with:
@@ -67,7 +67,7 @@ jobs:
   test-action-with-sha256-checksum-failure:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install devbox
         id: install-devbox
         uses: ./
@@ -85,7 +85,7 @@ jobs:
   test-action-with-sha256-checksum-on-mac:
     runs-on: macos-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install devbox
         uses: ./
         with:
@@ -98,7 +98,7 @@ jobs:
   test-action-with-extra-nix-config:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install devbox with extra nix config "user-agent-suffix = test-suffix"
         uses: ./
         with: