Bump actions/checkout from 6 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  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

@@ -24,7 +24,7 @@ jobs:
             os: ubuntu-latest
             arch: x86
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: julia-actions/setup-julia@v3
         with:
           version: ${{ matrix.version }}

.github/workflows/format_check.yml

@@ -13,7 +13,7 @@ jobs:
       - uses: julia-actions/setup-julia@latest
         with:
           version: '1'
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - name: Format check
         shell: julia --color=yes {0}
         run: |

.github/workflows/minlptests.yml

@@ -15,7 +15,7 @@ jobs:
         os: [ubuntu-latest, macOS-latest, windows-latest]
         arch: ['default']
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: julia-actions/setup-julia@v3
         with:
           version: ${{ matrix.version }}