Bump actions/checkout from 1 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 1 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v1...v4)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/TestJuliaVersions.yml

@@ -21,7 +21,7 @@ jobs:
         uses: julia-actions/setup-julia@latest
         with:
           version: ${{ matrix.julia-version }}         
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
 
       - name: Cache preCICE

.github/workflows/format.yml

@@ -15,7 +15,7 @@ jobs:
         with:
           version: ${{ matrix.julia-version }}
 
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
       - name: Install JuliaFormatter and format
         # This will use the latest version by default but you can set the version like so:
         #