📖 Remove example from --runtime-extension flag in clusterctl

[avaneesh634]

What this PR does / why we need it:
Remove example from --runtime-extension flag in clusterctl as clusterctl doesn't include any default runtime extensions.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #9796

/area documentation

[k8s-ci-robot]

Hi @avaneesh634. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[avaneesh634]

@fabriziopandini
@sbueringer

[killianmuldoon]

/ok-to-test

[avaneesh634]

/test pull-cluster-api-test-main

[sbueringer]

Thx!

/approve

[fabriziopandini]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: c64509b6b35b1d9afc5d0479f35ec3761b62b658

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fabriziopandini, sbueringer

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