remove: duplicate module imports

[parkyounghwan]

Thank you for providing the project.
I found a duplicate module while studying.

Thank you.

[googlebot]

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[tfdocsbot]

Preview and run these notebook edits with Google Colab:

• site/ko/guide/keras/overview.ipynb

Notebook diffs available on ReviewNB.com.

[tfdocsbot]

Reviewers added, please take a look.
@rickiepark, @cre8tor, @Choiuijin1125, @JKIsaacLee, @NoelBird, @wckim

When your review is finished, approve the pull request or include "LGTM" in your comment.

[parkyounghwan]

@googlebot I signed it!

…

On Fri, Jan 10, 2020 at 12:14 PM DocsBot ***@***.***> wrote: Preview and run these notebook edits with Google Colab: - site/ko/guide/keras/overview.ipynb <https://colab.research.google.com/github/parkyounghwan/docs/blob/master/site/ko/guide/keras/overview.ipynb> Notebook diffs <https://app.reviewnb.com/tensorflow/docs/pull/1375/files/> available on ReviewNB.com. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1375?email_source=notifications&email_token=AE5LEYV3YRVFONJI546TY7DQ47R2FA5CNFSM4KFBWK22YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEISRAGI#issuecomment-572854297>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AE5LEYXV2YDWY6CDA57Q4MDQ47R2FANCNFSM4KFBWK2Q> .

[googlebot]

CLAs look good, thanks!

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[lamberta]

Thanks for the fix!