Update authentication method in workflow

Replaced GITHUB_TOKEN with PAT for authentication in the workflow.

Author: Hau-Hau

.github/workflows/update-dotnet-version.yml

@@ -384,7 +384,7 @@ jobs:
             force: true
         - uses: ./.github/actions/put-pull-request
           with:
-            GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+            GITHUB_TOKEN: ${{ secrets.PAT }}
             title: Update .NET versions
             body: This PR updates .NET version used in project and pipelines.
             from: ${{ needs.init.outputs.branch }}