ci: Remove `--mcdc` from coverage runs #5433

Job	Run time
toolchains	5s
Ensure `Cargo.lock` contains all required dependencies	3s
check (ubuntu-latest, 1.76.0, debug)	3m 10s
check (ubuntu-latest, stable, debug)	2m 58s
check (ubuntu-latest, nightly, debug)	5m 9s
check (macos-latest, 1.76.0, debug)	3m 12s
check (macos-latest, stable, debug)	3m 6s
check (macos-latest, nightly, debug)	5m 11s
check (windows-latest, 1.76.0, debug)	6m 26s
check (windows-latest, stable, debug)	7m 6s
check (windows-latest, nightly, debug)	10m 1s
check (ubuntu-latest, stable, release)	4m 57s
bench	0s
	51m 24s

Provide feedback