Bump actions/checkout from 5 to 6 in the major group (#998)

Bumps the major group with 1 update: [actions/checkout](https://github.com/actions/checkout).


Updates `actions/checkout` from 5 to 6
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
       name: cargo test
       runs-on: ubuntu-latest-8-cores
       steps:
-        - uses: actions/checkout@v5
+        - uses: actions/checkout@v6
         - name: Install Rust
           uses: dtolnay/rust-toolchain@stable
         - uses: taiki-e/install-action@cargo-llvm-cov
@@ -44,7 +44,7 @@ jobs:
       name: Check for breaking API changes
       runs-on: ubuntu-latest-8-cores
       steps:
-        - uses: actions/checkout@v5
+        - uses: actions/checkout@v6
         - uses: taiki-e/install-action@just
         - name: Install Rust
           uses: dtolnay/rust-toolchain@stable
@@ -61,7 +61,7 @@ jobs:
       name: Check lints
       runs-on: ubuntu-latest-8-cores
       steps:
-        - uses: actions/checkout@v5
+        - uses: actions/checkout@v6
         - uses: taiki-e/install-action@just
         - name: Install Rust
           uses: dtolnay/rust-toolchain@stable
@@ -76,7 +76,7 @@ jobs:
       name: Check wasm
       runs-on: ubuntu-latest-8-cores
       steps:
-        - uses: actions/checkout@v5
+        - uses: actions/checkout@v6
         - uses: taiki-e/install-action@just
         - name: Install Rust
           uses: dtolnay/rust-toolchain@stable
@@ -91,7 +91,7 @@ jobs:
         name: cargo fmt
         runs-on: ubuntu-latest-8-cores
         steps:
-          - uses: actions/checkout@v5
+          - uses: actions/checkout@v6
           - name: Install Rust
             uses: dtolnay/rust-toolchain@stable
             with:
@@ -104,7 +104,7 @@ jobs:
         name: Check modeling-cmds can release
         runs-on: ubuntu-latest-8-cores
         steps:
-          - uses: actions/checkout@v5
+          - uses: actions/checkout@v6
           - name: Install Rust
             uses: dtolnay/rust-toolchain@stable
           - name: Dry-run a release of modeling-cmds
@@ -114,7 +114,7 @@ jobs:
       runs-on: ubuntu-latest
       steps:
         - name: Checkout
-          uses: actions/checkout@v5
+          uses: actions/checkout@v6
         - name: Run codespell
           uses: crate-ci/[email protected]
 
@@ -123,7 +123,7 @@ jobs:
       runs-on: ubuntu-latest
       steps:
         - name: Checkout
-          uses: actions/checkout@v5
+          uses: actions/checkout@v6
         - name: Install cargo-sort
           run: cargo install cargo-sort
         - name: Run check