Issue #4042: Add help for make clean target
Issue #4042: Add help for make clean target

Signed-off-by: Kevin Grigorenko <ffb4761cba839470133bee36aeb139f58d7dbaa9@myplaceonline.com>

jetstack-experimental/cert-manager,cert-manager/cert-manager,jetstack/cert-manager,jetstack/cert-manager,cert-manager/cert-manager,jetstack-experimental/cert-manager,jetstack-experimental/cert-manager,jetstack/cert-manager,cert-manager/cert-manager