fix typo in doc

[chrisjungsw]

Description

fix typo in doc

Fixed Issues (if relevant)

none

Contribution checklist

• [x] Pull request has a meaningful description of its purpose
• [x] All commits are accompanied by meaningful commit messages
• [x] All new or changed code is covered with unit/verification tests (if applicable)
• [ ] All automated tests passed successfully (all builds on Travis CI are green)
• [x] Changes to Framework doesn't have backward incompatible changes for tests or have related Pull Request with fixes to tests

[jilu1]

@magento import pull request to https://github.com/magento-commerce/magento2-functional-testing-framework

[magento-engcom-team]

@jilu1 the pull request successfully imported.