Link from README to tutorial broke after 2023.1

[gjsjohnmurray]

TestCoverage/README.md

Line 58 in adbe6ae

Generally speaking, set `^UnitTestRoot`, and then call `##class(TestCoverage.Manager).RunTest()` the same you would call `##class(%UnitTest.Manager).RunTest()`. For more information on InterSystems' %UnitTest framework, see the [tutorial](https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls?KEY=TUNT) and/or the [class reference for %UnitTest.Manager](https://docs.intersystems.com/irislatest/csp/documatic/%25CSP.Documatic.cls?PAGE=CLASS&LIBRARY=%25SYS&CLASSNAME=%25UnitTest.Manager).

I can find the referenced page in https://docs.intersystems.com/iris20231/csp/docbook/DocBook.UI.Page.cls?KEY=TUNT but not in later versions.