gh-103171: Document and test behaviour change in 3.11 for runtime-checkable protocols decorated with `@final`#103173

AlexWaygood wants to merge 2 commits intopython:mainpython/cpython:mainfrom

AlexWaygood:document-runtimecheckable-final-changeAlexWaygood/cpython:document-runtimecheckable-final-changeCopy head branch name to clipboard