chore(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] <support@github.com>

Author: dependabot[bot]

.github/workflows/cargo-docs.yml

@@ -9,7 +9,7 @@ jobs:
   publish:
     runs-on: [self-hosted, linux]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - run: git fetch --prune --unshallow
       - name: Install System Dependencies
         run: |

.github/workflows/cargo-test.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: [self-hosted, linux]
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           ref: ${{ github.event.pull_request.head.sha }}
       - run: git fetch --prune --unshallow

.github/workflows/draft-release.yml

@@ -15,7 +15,7 @@ jobs:
         runtime: ["interlay", "kintsugi"]
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Build ${{ matrix.runtime }} runtime
         id: srtool_build
@@ -46,7 +46,7 @@ jobs:
     runs-on: [self-hosted, linux]
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - uses: actions-rs/toolchain@v1
@@ -69,7 +69,7 @@ jobs:
     runs-on: [self-hosted, linux]
     needs: ["build-binary"]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Prepare
         id: prep
         run: |
@@ -127,7 +127,7 @@ jobs:
     needs: ["build-runtimes", "build-binary"]
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0