Fix doc for leader-elect-resource-lock flag

[ialidzhikov]

What type of PR is this?
/kind documentation

What this PR does / why we need it:
Currently https://kubernetes.io/docs/reference/command-line-tools-reference/kube-controller-manager/ does not list all supported values for leader-elect-resource-lock flag and wrongly states that the default value is endpoints (it should be endpointsleases).

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

Hi @ialidzhikov. Thanks for your PR.

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[ialidzhikov]

/assign @wojtek-t @liggitt

[liggitt]

/lgtm
/approve
/ok-to-test

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ialidzhikov, liggitt

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[ialidzhikov]

/retest

[ialidzhikov]

/sig api-machinery
/priority backlog