Bump actions/checkout from 4 to 5

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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/dotnetversionsweeper.yml

@@ -21,7 +21,7 @@ jobs:
 
     # Checkout the repo into the workspace within the VM
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     # If triggered manually, print the reason why
     - name: 'Print manual run reason'

.github/workflows/marp-pages.yml

@@ -25,7 +25,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Copy images
         run: mkdir build && cp -R slides/img build/img && cp -R slides/themes build/themes