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] <[email protected]>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -23,7 +23,7 @@ jobs:
     runs-on: [ubuntu-latest]
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - run: npm install
     - run: npm run-script build

.github/workflows/test.yml

@@ -20,7 +20,7 @@ jobs:
         emacs_version: [22.3, 23.4, 24.1, 24.2, 24.3, 24.4, 24.5, 25.1, 25.2, 25.3, 26.1, 26.2, 26.3, 27.1, 27.2, 28.1, 28.2, 29.1, 29.2, 29.3, 29.4, 30.1, 30.2, snapshot]
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - run: npm ci
     - run: npm run build

.github/workflows/update-snapshot.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         token: ${{ secrets.PAT }}
 

.github/workflows/update-stable.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         token: ${{ secrets.PAT }}