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]>

.github/workflows/CI.yml

@@ -25,7 +25,7 @@ jobs:
  - '1.6'
  - '1'
  steps:
- - uses: actions/checkout@v2
+ - uses: actions/checkout@v3
  - uses: julia-actions/setup-julia@v1
  with:
  version: ${{ matrix.version }}

.github/workflows/Downstream.yml

@@ -21,14 +21,14 @@ jobs:
  - {user: SciML, repo: DeepEquilibriumNetworks.jl, group: ALL}
 
  steps:
- - uses: actions/checkout@v2
+ - uses: actions/checkout@v3
  - uses: julia-actions/setup-julia@v1
  with:
  version: ${{ matrix.julia-version }}
  arch: x64
  - uses: julia-actions/julia-buildpkg@latest
  - name: Clone Downstream
- uses: actions/checkout@v2
+ uses: actions/checkout@v3
  with:
  repository: ${{ matrix.package.user }}/${{ matrix.package.repo }}
  path: downstream

.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:
  #