chore(deps): bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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/release-please-gha.yml

@@ -19,7 +19,7 @@ jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Generate GitHub App token
         id: app-token

.github/workflows/sonarcloud.yml

@@ -41,7 +41,7 @@ jobs:
         with:
           dotnet-version: |
             8.x 
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0 # Shallow clones should be disabled for a better relevancy of analysis
       - name: Cache SonarCloud packages

.github/workflows/validatePullRequest.yml

@@ -20,7 +20,7 @@ jobs:
       solutionName: Microsoft.Graph.Core.sln
       relativePath: ./src/Microsoft.Graph.Core
     steps:
-      - uses: actions/checkout@v4.1.7
+      - uses: actions/checkout@v6
 
       - name: Setup .NET
         uses: actions/setup-dotnet@v4
@@ -60,7 +60,7 @@ jobs:
     name: Validate Project for Trimming
     runs-on: windows-latest
     steps:
-      - uses: actions/checkout@v4.1.7
+      - uses: actions/checkout@v6
 
       - name: Setup .NET
         uses: actions/setup-dotnet@v4