Improve language in child README.md

[cmavr8]

Summary

Describe the goal of this PR. Mention any related Issue numbers.

Requirements (place an x in each [ ])

• [x] I've read and understood the Contributing Guidelines.

• [x] I've read and agree to the Code of Conduct.

• [x] I've not written tests to cover the new code and functionality included in this PR, because it's a minor language tweak.

• [x] I've read, agree to, and signed the Contributor License Agreement (CLA).

[CLAassistant]

All committers have signed the CLA.