Add comment that you must be registered

[jberkus]

Add text that clearly specifies that you must be a kubernetes contributor, and registered for the Summit, to attend the social. This has been a point of confusion both at prior Kubecons and currently based on email. The text needs to be there on the Social page.

/assign @mrbobbytables /area summit

[k8s-ci-robot]

@jberkus: The label(s) area/summit cannot be applied, because the repository doesn't have them.

In response to [this](https://github.com/kubernetes/contributor-site/pull/345): >Add text that clearly specifies that you must be a kubernetes contributor, and registered for the Summit, to attend the social. This has been a point of confusion both at prior Kubecons and currently based on email. The text needs to be there on the Social page. > >/assign @mrbobbytables >/area summit Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jberkus, mrbobbytables

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/kubernetes/contributor-site/blob/master/OWNERS)~~ [jberkus,mrbobbytables] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[jberkus]

/retest

[MadhavJivrajani]

/check-cla

[mrbobbytables]

/easycla