Fix broken article link (#3626)

Author: bradhowes

README.md

@@ -699,7 +699,7 @@ This library is released under the MIT license. See [LICENSE](LICENSE) for detai
 [gh-isowords]: https://github.com/pointfreeco/isowords
 [gh-discussions]: https://github.com/pointfreeco/swift-composable-architecture/discussions
 [swift-forum]: https://forums.swift.org/c/related-projects/swift-composable-architecture
-[testing-article]: https://pointfreeco.github.io/swift-composable-architecture/main/documentation/composablearchitecture/testing
+[testing-article]: https://pointfreeco.github.io/swift-composable-architecture/main/documentation/composablearchitecture/testingtca
 [faq-article]: https://pointfreeco.github.io/swift-composable-architecture/main/documentation/composablearchitecture/faq
 [dependencies-article]: https://pointfreeco.github.io/swift-composable-architecture/main/documentation/composablearchitecture/dependencymanagement
 [getting-started-article]: https://pointfreeco.github.io/swift-composable-architecture/main/documentation/composablearchitecture/gettingstarted