Label `kubernetes.io/bootstrapping` not registered / documented

[sftim]

This is a Bug Report

Problem:
There is a label, kubernetes.io/bootstrapping, that is not yet registered or documented.

Proposed Solution:
Update https://kubernetes.io/docs/reference/labels-annotations-taints/ to mention and document this label.

Page to Update:
https://kubernetes.io/docs/reference/labels-annotations-taints/

Additional Information:
Supporting evidence: https://docs.openshift.com/container-platform/4.7/authentication/using-rbac.html makes mention of the
kubernetes.io/bootstrapping and explains that it is used for some ClusterRoles / ClusterRoleBindings / Roles / RoleBindings.

/sig auth
/language en

/lifecycle frozen
/kind bug

[nitishfy]

/assign

[mehabhalodiya]

/triage accepted
/sig docs

[sftim]

/priority backlog