build(deps): bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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] <[email protected]>

Author: dependabot[bot]

.github/workflows/audit.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Run audit check
         uses: rustsec/audit-check@v2
         with:

.github/workflows/check.yml

@@ -19,7 +19,7 @@ jobs:
       matrix:
         rustc: [ nightly, stable ] # MSVR and current stable rustc
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.rustc }}
@@ -31,7 +31,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - uses: actions/cache@v4
         with:
           path: |
@@ -51,7 +51,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - uses: actions/cache@v4
         with:
           path: |
@@ -70,7 +70,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - uses: actions/cache@v3
         with:
           path: |
@@ -95,7 +95,7 @@ jobs:
       - test
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Install rust
         uses: dtolnay/rust-toolchain@stable
       - name: Run cargo publish

.github/workflows/docs.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           submodules: 'recursive'
 

.github/workflows/rust-clippy.yml

@@ -28,7 +28,7 @@ jobs:
       actions: read # only required for a private repository by github/codeql-action/upload-sarif to get the Action run status
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install Rust toolchain
         uses: dtolnay/rust-toolchain@stable