tools: Fix release-guide test mode
tools: Fix release-guide test mode

check-git-rw moved to cockpituous release/ many years ago. It's
installed into $PATH in the release container.

Closes #12659
mvollmer/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,garrett/cockpit,mvollmer/cockpit,deryni/cockpit,moraleslazaro/cockpit,garrett/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,cockpit-project/cockpit,garrett/cockpit,cockpit-project/cockpit,deryni/cockpit,cockpituous/cockpit,cockpituous/cockpit,martinpitt/cockpit,cockpituous/cockpit,deryni/cockpit,martinpitt/cockpit,cockpituous/cockpit,mvollmer/cockpit,deryni/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,deryni/cockpit,moraleslazaro/cockpit,garrett/cockpit,cockpituous/cockpit,mvollmer/cockpit,garrett/cockpit,cockpituous/cockpit,deryni/cockpit,martinpitt/cockpit,mvollmer/cockpit,deryni/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit