build(deps): bump actions/checkout from 3 to 6 (#270)

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...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/clippy.yml

@@ -21,7 +21,7 @@ jobs:
 
     steps:
       - name: Checkout repository code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v6
 
       # Cache Rust
       - uses: actions/cache@v3

.github/workflows/publish_nightly.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
       # Install buildx
       - name: Set up Docker Buildx
         id: buildx

.github/workflows/publish_stable.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
       # Install buildx
       - name: Set up Docker Buildx
         id: buildx

.github/workflows/tests.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
       # Install rust
       - uses: actions-rs/toolchain@v1
         with: