Bump actions/checkout from 5 to 6 (#15)

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/rust.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: |
           rustup toolchain install nightly --profile minimal --component rustfmt --component clippy
       - uses: Swatinem/rust-cache@v2
@@ -28,7 +28,7 @@ jobs:
   check-docs:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: |
           rustup toolchain install stable --profile minimal
       - uses: Swatinem/rust-cache@v2
@@ -42,7 +42,7 @@ jobs:
     needs: check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: |
           rustup toolchain install nightly --profile minimal
       - uses: Swatinem/rust-cache@v2
@@ -54,7 +54,7 @@ jobs:
     needs: check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: |
           rustup toolchain install stable --profile minimal
       - uses: Swatinem/rust-cache@v2