fixed typo
Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this [failed invocation](https://github.com/tensorflow/tensorflow/pull/62940/checks?check_run_id=21451947074) of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request. Hi @mahdiaslanimk  It looks like your PR relates to the Keras component. Please submit it to the github.com/keras-team/keras repository instead. Thank you!
@mihaimaruseac, @fchollet, @qlzh727  Right, I miss that part, sorry about it. Will remove approval Hi @mahdiaslanimk As mentioned above comments, please submit the PR to the github.com/keras-team/keras repository instead. Thank you!
Cc @fchollet, @qlzh727

Thank you @mihaimaruseac. 