Bump actions/checkout from 2 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...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-ci.yml

@@ -27,7 +27,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v6
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
@@ -45,7 +45,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v6
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
@@ -65,5 +65,5 @@ jobs:
   audit:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v6
     - uses: EmbarkStudios/cargo-deny-action@v2