build(deps): 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] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yaml

@@ -28,7 +28,7 @@ jobs:
     runs-on: ubuntu-24.04
     timeout-minutes: 10
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Setup Rust toolchain
         run: ./ci/install-rust.sh && rustup component add rustfmt
       - name: Check style
@@ -42,7 +42,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     timeout-minutes: 10
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: rustup update stable --no-self-update
       - uses: Swatinem/rust-cache@v2
       # Here we use the latest stable Rust toolchain already installed by GitHub
@@ -71,7 +71,7 @@ jobs:
     env:
       TOOLCHAIN: ${{ matrix.toolchain }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Setup Rust toolchain
         run: ./ci/install-rust.sh
 
@@ -133,7 +133,7 @@ jobs:
     env:
       TARGET: ${{ matrix.target }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Setup Rust toolchain
         run: ./ci/install-rust.sh
       - uses: Swatinem/rust-cache@v2
@@ -229,7 +229,7 @@ jobs:
     env:
       TARGET: ${{ matrix.target }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Setup Rust toolchain
         run: ./ci/install-rust.sh
       - uses: Swatinem/rust-cache@v2
@@ -273,7 +273,7 @@ jobs:
           - target: x86_64-unknown-netbsd
     timeout-minutes: 25
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: test on Solaris
         uses: vmactions/solaris-vm@v1.1.6
         if: contains(matrix.target, 'solaris')

.github/workflows/release.yaml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Install Rust (rustup)