build(deps): bump actions/checkout from 5 to 6 (#1069)

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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/release-please-gha.yml

@@ -19,7 +19,7 @@ jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Generate GitHub App token
         id: app-token

.github/workflows/validatePullRequest.yml

@@ -19,7 +19,7 @@ jobs:
       solutionName: Microsoft.Graph.Beta.sln
       projectName: src/Microsoft.Graph/Microsoft.Graph.Beta.csproj
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Setup .NET
         uses: actions/[email protected]
         with:
@@ -49,7 +49,7 @@ jobs:
         language: [ 'csharp' ]
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v4
       with: