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/rust.yml

@@ -27,7 +27,7 @@ jobs:
     container: quay.io/coreos-assembler/fcos-buildroot:testing-devel
     steps:
       - name: Check out repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install toolchain
         uses: dtolnay/rust-toolchain@v1
         with:
@@ -44,7 +44,7 @@ jobs:
     container: quay.io/coreos-assembler/fcos-buildroot:testing-devel
     steps:
       - name: Check out repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install toolchain
         uses: dtolnay/rust-toolchain@v1
         with:
@@ -61,7 +61,7 @@ jobs:
     container: quay.io/coreos-assembler/fcos-buildroot:testing-devel
     steps:
       - name: Check out repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Detect crate MSRV
         run: |
           msrv=$(cargo metadata --format-version 1 --no-deps | \
@@ -84,7 +84,7 @@ jobs:
     container: quay.io/coreos-assembler/fcos-buildroot:testing-devel
     steps:
       - name: Check out repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install toolchain
         uses: dtolnay/rust-toolchain@v1
         with:
@@ -106,7 +106,7 @@ jobs:
         channel: [beta, nightly]
     steps:
       - name: Check out repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install toolchain
         uses: dtolnay/rust-toolchain@v1
         with:
@@ -122,7 +122,7 @@ jobs:
     runs-on: windows-latest
     steps:
       - name: Check out repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install toolchain
         uses: dtolnay/rust-toolchain@v1
         with: