Bump actions/checkout from 3 to 5

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/docs.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
 
       - name: MkDocs
         run: |

.github/workflows/test.yml

@@ -33,7 +33,7 @@ jobs:
             experimental: true
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v5
 
     - uses: jcs090218/setup-emacs@master
       with: