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] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
             OPTIMISM_RPC_URL: ${{ secrets.OPTIMISM_RPC_URL }}
             POLYGON_RPC_URL: ${{ secrets.POLYGON_RPC_URL }}
         steps:
-            - uses: actions/checkout@v3
+            - uses: actions/checkout@v6
               with:
                   submodules: recursive
 

.github/workflows/publish.yml

@@ -28,7 +28,7 @@ jobs:
               uses: foundry-rs/foundry-toolchain@v1
               with:
                   version: nightly
-            - uses: actions/checkout@v2
+            - uses: actions/checkout@v6
               with:
                   ref: ${{ github.ref }}
                   fetch-depth: 0