build(deps): bump actions/checkout from 4 to 5

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/Downgrade.yml

@@ -18,7 +18,7 @@ jobs:
         downgrade_mode: ['alldeps']
         julia-version: ['1.10']
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: julia-actions/setup-julia@v2
         with:
           version: ${{ matrix.julia-version }}

.github/workflows/Downstream.yml

@@ -19,14 +19,14 @@ jobs:
         package:
           - {user: SciML, repo: ModelingToolkit.jl}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: julia-actions/setup-julia@v2
         with:
           version: ${{ matrix.julia-version }}
           arch: x64
       - uses: julia-actions/julia-buildpkg@latest
       - name: Clone Downstream
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           repository: ${{ matrix.package.user }}/${{ matrix.package.repo }}
           path: downstream

.github/workflows/SpellCheck.yml

@@ -8,6 +8,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout Actions Repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Check spelling
         uses: crate-ci/[email protected]