Bump actions/checkout from v5 to v6

Updated the GitHub Actions checkout action to version 6 across
the workflow file to use the latest major version. This upgrade
applies to both the build job and the deployment job, ensuring
the workflow benefits from the latest bug fixes, performance
improvements, and features available in v6.
[release]

Author: madskristensen

.github/workflows/build.yaml

@@ -24,7 +24,7 @@ jobs:
       VsixManifestSourcePath: src\source.extension1.cs
 
     steps:
-    - uses: actions/checkout@5
+    - uses: actions/checkout@6
 
     - name: Setup MSBuild
       uses: microsoft/setup-msbuild@v3
@@ -59,7 +59,7 @@ jobs:
     runs-on: windows-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Download Package artifact
         uses: actions/download-artifact@v8