Bump the version of llvm that clang tidy runs against to 20#372

mcbarton merged 1 commit intocompiler-research:maincompiler-research/xeus-cpp:mainfrom

mcbarton:Update-clang-tidy-workflow-to-clang-tidy-20mcbarton/xeus-cpp:Update-clang-tidy-workflow-to-clang-tidy-20Copy head branch name to clipboard