Bump actions/checkout from 2.4.0 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 2.4.0 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/v2.4.0...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>

.github/workflows/flake-check.yml

@@ -11,7 +11,7 @@ jobs:
     outputs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}
     steps:
-      - uses: actions/checkout@v2.4.0
+      - uses: actions/checkout@v3
         with:
           # Nix Flakes doesn't work on shallow clones
           fetch-depth: 0
@@ -31,7 +31,7 @@ jobs:
     strategy:
       matrix: ${{fromJSON(needs.flake-checks.outputs.matrix)}}
     steps:
-      - uses: actions/checkout@v2.4.0
+      - uses: actions/checkout@v3
         with:
           # Nix Flakes doesn't work on shallow clones
           fetch-depth: 0

.github/workflows/test-develop-classic.yml

@@ -11,7 +11,7 @@ jobs:
         os: [ ubuntu-latest, macos-latest ]
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - uses: cachix/install-nix-action@v16
       with:
         nix_path: nixpkgs=channel:nixos-unstable

.github/workflows/test-develop-flakes.yml

@@ -11,7 +11,7 @@ jobs:
         os: [ ubuntu-latest, macos-latest ]
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
       with:
           # Nix Flakes doesn't work on shallow clones
           fetch-depth: 0

.github/workflows/update-flake-lock.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Install Nix
         uses: cachix/install-nix-action@v16
         # with: