black formatting for utils/tensorboard (#76396)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/76396
Reviewed By: Reubend
Differential Revision: D35945748
Pulled By: edward-io
fbshipit-source-id: ffee22e88aaf49eb98b3e2eb6624a2dadb8ef754
(cherry picked from commit 6b5656b7c081cd69135b54f7d13d02c1c361b696)
