Bump actions/checkout from 1 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 1 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v1...v3)

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

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

Author: dependabot[bot]

.github/workflows/CI.yml

@@ -17,7 +17,7 @@ jobs:
           - '1'
           - '1.6'
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: julia-actions/setup-julia@v1
         with:
           version: ${{ matrix.version }}

.github/workflows/FormatCheck.yml

@@ -21,7 +21,7 @@ jobs:
         with:
           version: ${{ matrix.julia-version }}
 
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v3
       - name: Install JuliaFormatter and format
         # This will use the latest version by default but you can set the version like so:
         #