Dependabot(deps): Bump actions/checkout from 2 to 3 (#441)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2...v3)

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

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/check-flake-files.yml

@@ -19,7 +19,7 @@ jobs:
     steps:
 
     - name: Checking out the repository
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
 
     - name: Setup
       uses: ./.github/actions/common-setup

.github/workflows/frontend.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checking out the repository
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
 
     - name: Setup
       uses: ./.github/actions/common-setup

.github/workflows/import-flakes.yml

@@ -25,7 +25,7 @@ jobs:
     steps:
 
     - name: Checking out the repository
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
 
     - name: Setup
       uses: ./.github/actions/common-setup

.github/workflows/import-nixpkgs.yml

@@ -26,7 +26,7 @@ jobs:
 
     steps:
     - name: Checking out the repository
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
 
     - name: Setup
       uses: ./.github/actions/common-setup