Remove the word "master" from our codebase

[vincepri]

• https://github.com/kubernetes-sigs/kubebuilder/blob/38343942a397a02559bfdd46f3d31257d1561f98/docs/book/src/reference/kind.md "with 1 master"
• https://github.com/kubernetes-sigs/kubebuilder/blob/master/docs/book/getting_started/installation_and_setup.md

[fejta-bot]

Issues go stale after 90d of inactivity. Mark the issue as fresh with /remove-lifecycle stale. Stale issues rot after an additional 30d of inactivity and eventually close.

If this issue is safe to close now please do so with /close.

Send feedback to sig-testing, kubernetes/test-infra and/or fejta. /lifecycle stale

[vincepri]

/lifecycle frozen

[mk46]

/assign