man: Explain that cockpit.conf(5) does not exist by default
man: Explain that cockpit.conf(5) does not exist by default

Closes #14141
moraleslazaro/cockpit,garrett/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,garrett/cockpit,mvollmer/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,garrett/cockpit,deryni/cockpit,martinpitt/cockpit,deryni/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,deryni/cockpit,mvollmer/cockpit,deryni/cockpit,mvollmer/cockpit,deryni/cockpit,garrett/cockpit,cockpit-project/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,deryni/cockpit,garrett/cockpit,martinpitt/cockpit,martinpitt/cockpit,martinpitt/cockpit,deryni/cockpit,cockpit-project/cockpit