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/publishdocs.yaml

@@ -14,7 +14,7 @@ jobs:
     if: github.repository_owner == 'INCF'
     steps:
     - name: Checkout master
-      uses: actions/checkout@v4
+      uses: actions/checkout@v5
 
     - name: Deploy docs
       uses: mhausenblas/mkdocs-deploy-gh-pages@master

.github/workflows/update_spreadsheet.yml

@@ -24,7 +24,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v4
+      uses: actions/checkout@v5
 
     - name: Set up Python
       uses: actions/setup-python@v5

.github/workflows/validate.yml

@@ -16,7 +16,7 @@ jobs:
     if: github.repository_owner == 'INCF'
     runs-on: ubuntu-latest
     steps:
-    -   uses: actions/checkout@v4
+    -   uses: actions/checkout@v5
     -   name: Setup Node
         uses: actions/setup-node@v4
         with: