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] <support@github.com>

Author: dependabot[bot]

.github/workflows/CI.yml

@@ -23,7 +23,7 @@ jobs:
     name: Python lint + typecheck
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: "3.12"
@@ -41,7 +41,7 @@ jobs:
     name: Rust fmt + clippy
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: rustfmt, clippy
@@ -60,7 +60,7 @@ jobs:
         os: [ubuntu-latest, macos-latest, windows-latest]
         python: ["3.9", "3.11", "3.13"]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           submodules: recursive
       - uses: actions/setup-python@v6

.github/workflows/release.yml

@@ -29,7 +29,7 @@ jobs:
       matrix:
         target: [x86_64, aarch64]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: "3.12"
@@ -66,7 +66,7 @@ jobs:
       matrix:
         target: [x86_64, aarch64]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: "3.12"
@@ -93,7 +93,7 @@ jobs:
       matrix:
         target: [x64, aarch64]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: "3.12"
@@ -118,7 +118,7 @@ jobs:
     name: sdist
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Build sdist
         uses: PyO3/maturin-action@v1