Fix kubectl rename-context description grammar

[sftim]

What type of PR is this?
/kind bug
/priority backlog
/sig docs

What this PR does / why we need it:
This PR fixes a grammar nit in the help for kubectl config rename-context

Which issue(s) this PR fixes:
Fixes #77402

Special notes for your reviewer:
(my first PR to this repo - let me know if this does need a release note).

Does this PR introduce a user-facing change?:
Sort of, but it's super tiny.

NONE

[k8s-ci-robot]

Hi @sftim. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[mattjmcnaughton]

Congrats on your first pr :)

/ok-to-test
/lgtm

[mattjmcnaughton]

/assign @apelisse

[apelisse]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: apelisse, sftim

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