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.yml

@@ -24,15 +24,15 @@ jobs:
     name: rustfmt
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: sfackler/actions/rustup@master
       - uses: sfackler/actions/rustfmt@master
 
   clippy:
     name: clippy
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: sfackler/actions/rustup@master
       - run: echo "version=$(rustc --version)" >> $GITHUB_OUTPUT
         id: rust-version
@@ -58,7 +58,7 @@ jobs:
     name: min-version
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       # Remember to also update `--rust-target` in `openssl-sys/build/run_bindgen.rs`
       - uses: sfackler/actions/rustup@master
         with:
@@ -96,7 +96,7 @@ jobs:
     name: windows-vcpkg-${{ matrix.os.arch }}
     runs-on: ${{ matrix.os.runner }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: sfackler/actions/rustup@master
       - run: echo "version=$(rustc --version)" >> $GITHUB_OUTPUT
         id: rust-version
@@ -124,7 +124,7 @@ jobs:
     name: macos-homebrew
     runs-on: macos-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: sfackler/actions/rustup@master
       - run: echo "version=$(rustc --version)" >> $GITHUB_OUTPUT
         id: rust-version
@@ -235,7 +235,7 @@ jobs:
         CARGO_TARGET_ARM_UNKNOWN_LINUX_GNUEABIHF_AR: arm-linux-gnueabihf-ar
         CARGO_TARGET_ARM_UNKNOWN_LINUX_GNUEABIHF_RUNNER: qemu-arm -L /usr/arm-linux-gnueabihf
       steps:
-        - uses: actions/checkout@v5
+        - uses: actions/checkout@v6
         - uses: sfackler/actions/rustup@master
         - run: echo "version=$(rustc --version)" >> $GITHUB_OUTPUT
           id: rust-version