chore: Bump actions/checkout from 5 to 6 (#80)

Bumps [actions/checkout](https://github.com/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
...

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

@@ -33,7 +33,7 @@ jobs:
             downgrade: true
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@v2
         id: setup-julia
         with:
@@ -61,7 +61,7 @@ jobs:
         version: ['1']
         downgrade: [false, true]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@v2
         id: setup-julia
         with:

.github/workflows/Invalidations.yml

@@ -19,12 +19,12 @@ jobs:
     - uses: julia-actions/setup-julia@v2
       with:
         version: '1'
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: julia-actions/julia-buildpkg@v1
     - uses: julia-actions/julia-invalidations@v1
       id: invs_pr
 
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         ref: ${{ github.event.repository.default_branch }}
     - uses: julia-actions/julia-buildpkg@v1

.github/workflows/format_check.yml

@@ -15,7 +15,7 @@ jobs:
       - uses: julia-actions/setup-julia@latest
         with:
           version: 1
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Install JuliaFormatter
         run: |
           using Pkg