Move CI runners away from `macOS-10.15` because of sunsetting by Github.#7028

Merged

NlightNFotis merged 2 commits intodiffblue:developfrom

NlightNFotis:move_ci_runners_macos_11

Jul 26, 2022

Commits on Jul 22, 2022

Move CI runners away from `macOS-10.15` because of sunsetting by Github.
NlightNFotis
committed
Delete extraneous `check-macos-11-cmake-clang` job.
NlightNFotis
committed