[hotfix][docs] Fix typo

[ghost]

[hotfix][docs] fix typos

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Last check on commit 9430aca (Tue Aug 27 09:19:15 UTC 2019)

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• ❓ 1. The [description] looks good.
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CI report:

• 9430aca : SUCCESS Build

[1u0]

Hi @yngwiewang,
Please close this PR and include this changes as one commit in your #9538 PR.

[ghost]

Hi @yngwiewang,
Please close this PR and include this changes as one commit in your #9538 PR.

OK, thanks.