Bump actions/checkout from 5 to 6 (#289)

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

Author: dependabot[bot]

.github/workflows/test.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - uses: Swatinem/rust-cache@v2
         with:
@@ -53,7 +53,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - uses: Swatinem/rust-cache@v2
         with:
@@ -67,7 +67,7 @@ jobs:
           cargo install --debug --locked --version 0.5.0 mdbook
 
       - name: Checkout ${{ matrix.repo }}
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: ${{ matrix.repo }}
           ref: ${{ matrix.ref }}
@@ -86,7 +86,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Install nightly Rust
         run: rustup default nightly
@@ -130,7 +130,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - uses: Swatinem/rust-cache@v2
 
@@ -142,7 +142,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Setup Rust nightly
         run: rustup default stable