Update GitHub actions to set `not planned` as the `state_reason` when automatically closing issues

[Colengms]

This issue is tracking updating vscode-cpptools GitHub actions with the latest implementation from the vscode-github-triage-actions repo.

The vscode-cpptools repo uses actions based on those used by the vscode, from the above repo. I had been waiting until this improvement was made to vscode's actions, to integrate their changes. This is now complete: https://github.com/microsoft/vscode-github-triage-actions/issues/82 .