ci: Switch CI to macos 15 runner #335

Job	Run time
Build clio (macos15c16, Release, false)	1s
Build clio (heavy, Release, true, rippleci/clio_ci:latest)	23m 28s
Build clio (heavy, Debug, true, rippleci/clio_ci:latest)	15m 5s
run_tests	0s
nightly_release	0s
build_and_publish_docker_image	0s
create_issue_on_failure	0s
	38m 34s

Provide feedback