Fix leak of ThreadSafeData in AsyncProgressWorkerBase<DataType>

PR-URL: https://github.com/nodejs/node-addon-api/pull/795
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Gabriel Schulhof <gabriel.schulhof@intel.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

• Commit 8bb540e
• #9: [pull] master from nodejs:master
• Branch master

pull[bot]