Nightly windows build is failing due to missing commit datetime

[seanpmorgan]

Our builds are failing due to the windows wheels not getting their commit datetime appended to the whl names:

Uploading tensorflow_addons-0.12.0.dev0-cp36-cp36m-win_amd64.whl

  0%|          | 0.00/910k [00:00<?, ?B/s]
 62%|██████▏   | 568k/910k [00:00<00:00, 5.42MB/s]
100%|██████████| 910k/910k [00:06<00:00, 150kB/s] 
NOTE: Try --verbose to see response content.
HTTPError: 400 Bad Request from https://upload.pypi.org/legacy/
File already exists. See https://pypi.org/help/#file-name-reuse for more information.

https://github.com/tensorflow/addons/runs/1317714967?check_suite_focus=true

[seanpmorgan]

EDIT --- Actually the full NIGHTLY_FLAG is missing for the windows builds. Not sure why this isn't working anymore:
https://github.com/tensorflow/addons/blob/master/.github/workflows/release.yml#L54

Thx @bhack