Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/checks.yml

@@ -30,7 +30,7 @@ jobs:
 
     steps:
 
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
 
@@ -53,7 +53,7 @@ jobs:
       with:
         cabal-version: "3.10.1.0"
 
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Cabal check
       run: ./scripts/ci/check-cabal-files.sh
@@ -65,7 +65,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Check README badges
       run: |
@@ -104,7 +104,7 @@ jobs:
         mkdir -p ${HOME}/.local/bin
         mv cabal-plan ${HOME}/.local/bin/cabal-plan
 
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Diff plans
       run: GH=1 ./scripts/release/cabal-plan-diff.sh
@@ -115,7 +115,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: serokell/xrefcheck-action@v1
       with:
         xrefcheck-version: 0.3.1

.github/workflows/ci.yml

@@ -53,7 +53,7 @@ jobs:
       CABAL: "3.12.1.0"
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Check CDDLs up-to-date with Blueprints
       continue-on-error: true
@@ -212,7 +212,7 @@ jobs:
         ghc: ["9.6.7", "9.10.2"]
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Install base libraries
       uses: input-output-hk/actions/base@latest
@@ -289,7 +289,7 @@ jobs:
     strategy:
        fail-fast: false
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-node@v6
         with:

.github/workflows/documentation.yml

@@ -26,7 +26,7 @@ jobs:
        fail-fast: false
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v6
         with:
           node-version: 18