Typo in the README.md file

[abrarShariar]

There is a small typo ("and" is mentioned twice) in the README.md file

https://github.com/apple/swift-corelibs-xctest/blob/main/README.md

To contribute, you'll need to be able to build this project and and run its test suite. The easiest way to do so is via the Swift build script.